I have looked at many different code snippets on this site looking that would show me how to do something that should be fairly simple once I have the knowledge.
I want to query a database table for an array of values and then populate a combobox with those results.
Here is what I have so far:
Public Sub getMachines()
Try
Dim SQL As String = "SELECT MachineName from machine"
Form1.machineName.DisplayMember = "Text"
Dim tb As New DataTable
tb.Columns.Add("Text", GetType(String))
Using cn As New MySqlConnection(ConnectionString)
Using cmd As New MySqlCommand(SQL, cn)
For Each cmd As String In cmd
'I want to add each value found in the database to "tb.Rows.Add"
'tb.Rows.Add(???)
Next
Form1.machineName.DataSource = tb
cn.Open()
cmd.ExecuteNonQuery()
End Using
cn.Close()
End Using
Catch ex As MySqlException
MsgBox(ex.Message)
End Try
End Sub
I proceeded much like you did. I used the Load method of the DataTable. It is not necessary to set the column name and type. The name of the column is taken from the Select statement and the datatype is inferred by ADO.net from the first few records.
Luckily a DataTable can be an Enumerable using the .AsEnumnerable method. Then we can use Linq to get all the values from the MachineName column. Calling .ToArray causes the Linq to execute. If you hold your cursor over names on this line you will see that the datatype is String(). Just what we need to fill a combo box.
Code for a class called DataAccess
Private ConnectionString As String = "Your Connection String"
Public Function GetMachineNames() As String()
Dim tb As New DataTable
Dim SQL As String = "SELECT MachineName from machine;"
Using cn As New MySqlConnection(ConnectionString)
Using cmd As New MySqlCommand(SQL, cn)
cn.Open()
dt.Load(cmd.ExecuteReader)
End Using
End Using
Dim names = dt.AsEnumerable().Select(Function(x) x.Field(Of String)("MachineName")).ToArray()
Return names
End Function
In the form load you combo box like this.
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Dim DatAcc As New DataAccess()
Dim arr = DatAcc.GetMachineNames()
machineName.DataSource = arr
End Sub
If you just want the MachineName to be displayed in the ComboBox, then just use that as the DisplayMember; don't bother creating another column called Text.
Public Sub getMachines()
Try
Dim cmd As String = "SELECT MachineName from machine"
Dim ds As New DataSet()
Using con As New MySqlConnection(ConnectionString)
Using da As New MySqlDataAdapter(cmd, con)
da.Fill(ds)
With Form1.machineName
.DisplayMember = "MachineName"
.ValueMember = "MachineName"
.DataSource = ds
End With
End Using
End Using
Catch ex As MySqlException
MsgBox(ex.Message)
End Try
End Sub
I'll show a few examples, including using parameters, since that is important.
First up, a quick translation to run the existing query and loop through the results:
Public Sub getMachines()
Try
Dim SQL As String = "SELECT MachineName from machine"
Using cn As New MySqlConnection(ConnectionString), _
cmd As New MySqlCommand(SQL, cn)
cn.Open()
Using rdr As MySqlDatareader = cmd.ExecuteReader
While rdr.Read()
Form1.machineName.Items.Add(rdr("MachineName"))
End While
End Using
End Using
Catch ex As MySqlException
MsgBox(ex.Message)
End Try
End Sub
But better practice for a method like this is to isolate data access for the UI. This method should return results to the caller, which can decide what do with them. So I'll show two methods: one to get the data, and the other to loop through it and set up the combobox:
Private Function GetMachines() As DataTable
'No try/catch needed here. Handle it in the UI level, instead
Dim SQL As String = "SELECT MachineName from machine"
Dim result As New DataTable
Using cn As New MySqlConnection(ConnectionString), _
cmd As New MySqlCommand(SQL, cn),
da As New MySqlDataAdapter(cmd)
da.Fill(result)
End Using
Return result
End Function
Public Sub LoadMachines()
Try
For Each item As DataRow in getMachines().Rows
Form1.machineName.Items.Add(item("MachineName"))
Next
Catch ex As MySqlException
MsgBox(ex.Message)
End Try
End Sub
Or, we can use DataBinding:
Private Function GetMachines() As DataTable
Dim SQL As String = "SELECT MachineName from machine"
Dim result As New DataTable
Using cn As New MySqlConnection(ConnectionString), _
cmd As New MySqlCommand(SQL, cn),
da As New MySqlDataAdapter(cmd)
da.Fill(result)
End Using
Return result
End Function
Public Sub LoadMachines()
Try
Form1.machineName.DisplayMember = "FirstName";
Form1.machineName.ValueMember = "City"
Form1.machineName.DataSource = GetMachines()
Catch ex As MySqlException
MsgBox(ex.Message)
End Try
End Sub
If you ever want to use a filter, you might do this (notice the overloading):
Private Function GetMachines(ByVal machineFilter As String) As DataTable
Dim SQL As String = "SELECT MachineName from machine WHERE MachineName LIKE #Filter"
Dim result As New DataTable
Using cn As New MySqlConnection(ConnectionString), _
cmd As New MySqlCommand(SQL, cn),
da As New MySqlDataAdapter(cmd)
'Match the MySqlDbType to your actual database column type and length
cmd.Parameters.Add("#Filter", MySqlDbType.VarString, 30).Value = machineFilter
da.Fill(result)
End Using
Return result
End Function
Private Function GetMachines(ByVal machineFilter As String) As DataTable
Return GetMachines("%")
End Function
Query parameters like that are very important, and if you were doing string concatenation to accomplish this kind of thing on your old platform, you were doing very bad things there, too.
Finally, let's get fancy. A lot of the time, you really don't want to load an entire result set into RAM, as is done with a DataTable. That can be bad. Instead, you'd like be able to stream results into memory and only work with one at a time, minimizing RAM use. In these cases, you get to play with a DataReader... but returning a DataReader object from within a Using block (which is important) doesn't work that well. To get around this, we can use functional programming concepts and advanced language features:
Private Iterator Function GetMachines(ByVal machineFilter As String) As IEnumerable(Of String)
Dim SQL As String = "SELECT MachineName from machine WHERE MachineName LIKE #Filter"
Using cn As New MySqlConnection(ConnectionString), _
cmd As New MySqlCommand(SQL, cn)
'Match the MySqlDbType to your actual database column type and length
cmd.Parameters.Add("#Filter", MySqlDbType.VarString, 30).Value = machineFilter
cn.Open()
Using rdr As MySqlDatareader = cmd.ExecuteReader
While rdr.Read()
Dim result As String = rdr("MachineName")
Yield Return result
End While
End Using
End Using
Return result
End Function
Private Function GetMachines() As IEnumerable(Of String)
Return GetMachines("%")
End Function
I currently have the following code in my project which populates a DataGridView object with the results of an SQL query.
Sub PerformQuery(ByVal SQLText As String)
Dim DbConnection As New OleDb.OleDbConnection(createConnectionString)
Dim SQLQuery As String = SQLText
Dim Adapter As New OleDb.OleDbDataAdapter(SQLQuery, DbConnection)
Try
Using Table As New DataTable
Adapter.Fill(Table)
Table.Locale = Globalization.CultureInfo.InvariantCulture
DbConnection.Close()
DataGridView1.DataSource = Table
End Using
Catch ex As Exception
MsgBox(ex.Message)
End Try
End Sub
Elsewhere in my project I can create a DataSet object using the code
Dim ds As New DataSet
And then extract data from it using code like:
MaxRows = ds.Tables("Dataset_Users").Rows.Count
Rather than populating a DataGridView, how can I use the PerformQuery code to create a dataset?
Thank you in advance for your help.
I think you are after the following:
Try
Dim ds As New DataSet
Using Table As New DataTable
Adapter.Fill(Table)
Table.Locale = Globalization.CultureInfo.InvariantCulture
DbConnection.Close()
DataGridView1.DataSource = Table
ds.Table.Add(Table)
End Using
Catch ex As Exception
MsgBox(ex.Message)
End Try
Or as in your example you was after the Number of rows in the dataset you can do the same with the DataTable, For Example:
Try
Dim MaxRows As Integer
Using Table As New DataTable
Adapter.Fill(Table)
Table.Locale = Globalization.CultureInfo.InvariantCulture
DbConnection.Close()
DataGridView1.DataSource = Table
'' Getting the number of rows in the DataTable
MaxRows = Table.Rows.Count
End Using
Catch ex As Exception
MsgBox(ex.Message)
End Try
Think in a more functional style. Return the table instead of setting to grid. While we're here, let's update the method so you don't have to write queries anymore that leave you wide open to sql injection attacks:
Function PerformQuery(ByVal SQLText As String, ByVal ParamArray Parameters() As OleDbParameter) As DataTable
Dim result As New DataTable()
Using cn As New OleDb.OleDbConnection(createConnectionString), _
cmd As New OleDb.OleDbCommand(SQLText, cn), _
Adapter As New OleDb.OleDbDataAdapter(cmd, cn)
If Parameters IsNot Nothing AndAlso Parameters.Length > 0 Then
cmd.Parameters.AddRange(Parameters)
End If
Adapter.Fill(result)
End Using
Return Result
End Function
Note that I also removed the error handling and locale code. You still need to do that stuff, but when you want to just return a datatable instead of interact directly with the user interface in a method you have effectively moved your code to a lower level of abstraction. When you do that, you probably don't want to deal with the error handling at this lower level any more; instead let the exceptions bubble up where you can handle them closer to the user interface.
Now you call the updated method like this:
Dim sql As String = "SELECT * FROM Customers WHERE CustomerID = ?"
Dim CustID As New OleDb.OleDbParameter("CustomerId", OleDbType.Integer)
CustID.Value = 123456
Try
DataGridView1.DataSource = PerformQuery(sql, CustID)
Catch Ex As Excpetion
MsgBox(Ex.Message)
End Try
Insert new row inside DataGridView
This answer makes it seem like the database should update with the rows.add
Some other sites have instructions, but form a perspective of creating the database from scratch. I already have a database and just want the stupid thing to accept new data.
Here's what I have done:
Private Sub InitializeDataGridView()
Try
' Set up the DataGridView.
With Me.DataGridView1
' Automatically generate the DataGridView columns.
.AutoGenerateColumns = True
' Set up the data source.
'bindingSource1.DataSource = GetData("SELECT * FROM Places and Stuff")
MyTable = GetData("SELECT * FROM Places and Stuff")
'MyDataSet = bindingSource1.DataSource
'MyTable = MyDataSet.Tables(0)
.DataSource = MyTable
' Automatically resize the visible rows.
.AutoSizeRowsMode = DataGridViewAutoSizeRowsMode.DisplayedCellsExceptHeaders
' Set the DataGridView control's border.
.BorderStyle = BorderStyle.Fixed3D
' Put the cells in edit mode when user enters them.
.EditMode = DataGridViewEditMode.EditOnEnter
' Disables Add New Row
.AllowUserToAddRows = False
End With
Catch ex As SqlException
MessageBox.Show(ex.ToString, _
"ERROR", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
System.Threading.Thread.CurrentThread.Abort()
End Try
End Sub
I am binding the DGV to a table. It seems like maybe I need a dataset somewhere to update but I cannot figure out how to populate a dataset with a table that is also a sql database. You can also see where I have played around with other datasets/datatables etc.
I also got my datagridview to add a row but the database is being lazy:
Private Sub btnAdd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAdd.Click
'Determine Last Row Index
Dim dgvrowCnt As Integer = DataGridView1.Rows.Count - 1
If DataGridView1.Rows.Count > 0 Then
Dim myRow As DataRow = MyTable.NewRow
myRow(0) = DataGridView1.Rows(dgvrowCnt).Cells(0).Value + 1
MyTable.Rows.Add(myRow)
Else
Dim myRow As DataRow = MyTable.NewRow
myRow(0) = 230
MyTable.Rows.Add(myRow)
End If
End Sub
I am a little saddened by not being able to use myRow("<column name here>") = 230 but I'll have to get over it I guess.
I have tried refreshing and checking the table to see if my form needs to be refreshed, but that doesn't seem to be the case.
This page http://support.microsoft.com/kb/301248 has 2 lines and claims it does what I am hoping for:
Dim objCommandBuilder As New SwlCammandBuilder(daAuthors)
daAuthors.Update(dsPubs, "Authors")
I cannot get my table into a dataset as shown in the binding lines of my example.
It seems that you haven't understood a fundamental concept of ADO.NET. The DataTable and other objects like the DataSet are 'disconnected' objects, meaning that adding/updating and removing rows doesn't update/insert/delete the database table.
You need to create an SqlCommand, prepare its command text and then Execute a query to update your db (other methods include using an SqlDataAdapter and its Update method)
For example, to insert a single row in a datatable your code should be something like this
Using con = New SqlConnection(.....constringhere...)
Using cmd = new SqlCommand("INSERT INTO table1 (field1) values (#valueForField)", con)
con.Open()
cmd.Parameters.AddWithValue("#valueForField", newValue)
cmd.ExecuteNonQuery()
End Using
End Using
A more complete tutorial could be found here
Instead this could be a pseudocode to use a SqlDataAdapter and a SqlCommandBuilder to automate the construction of the commands required to store your changes back to the database
' Keep the dataset and the adapter at the global class level'
Dim da As SqlDataAdapter = Nothing
Dim ds As DataSet
Private Function GetData(ByVal sqlCommand As String) As DataSet
ds As New DataSet()
Dim connectionString As String = "Data Source=...."
Using con = New SqlConnection(connectionString)
conn.Open()
Using command = New SqlCommand(sqlCommand, con)
Using da = New SqlDataAdapter(command)
da.Fill(ds)
End Using
End Using
End Using
Return ds
End Function
Use the first table inside the DataSet returned by GetData as Datasource of the grid (or just use the whole dataset)
.DataSource = GetData(.......).Tables(0)
' Add a new button to submit changes back to the database'
Private Sub btnSave_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAdd.Click
Dim builder = New SqlCommandBuilder(da)
da.UpdateCommand = builder.GetUpdateCommand()
da.InsertCommand = builder.GetInsertCommand()
da.DeleteCommand = builder.GetDeleteCommand()
da.Update(ds)
End Sub
Please, note that I cannot test this code, and I offer it as a pseudocode without any error checking required by a more robust application.
I was developing an application using oop concept.I have a class that has 2 attributes and have Get and Set methods namely WorkItemNumber and Description.
On the client side i have a list box used to populate the work items based on their description.Here's the code i wrote in the class o read items from the database.
Public Sub LoadWorkItem()
' Load the data.
' Select records.
Dim oWorkItem As WorkItem = New WorkItem()
Dim conn As New OleDbConnection
Dim data_reader As OleDbDataReader
conn = oWorkItem.GetDbConnection()
Dim cmd As New OleDbCommand("SELECT * FROM work_item ORDER BY [work item number]", conn)
data_reader = cmd.ExecuteReader()
'ListBox1.Items.Clear()
If data_reader.HasRows = True Then
Do While data_reader.Read()
WorkItemNumber = data_reader.Item("work item number")
Description = data_reader.Item("description")
Loop
End If
data_reader.Close()
data_reader = Nothing
cmd.Dispose()
cmd = Nothing
conn.Close()
conn.Dispose()
End Sub
How do i populate the listbox using the code,and if there's any improvement on the code please do tell me as well.Thank you
To poulate your ListBox, do this...
ListBox1.Item.Clear()
If data_reader.HasRows Then
Do While data_reader.Read()
WorkItemNumber = data_reader.Item("work item number")
Description = data_reader.Item("description")
ListBox1.Items.Add(New ListItem(Description, WorkItemNumber)
Loop
End If
As far as improvements, start by using a Using statement for the DB connection. In your code, if there is an exception while the database connection is open, it will never get closed. This is better...
Using conn As OleDbConnection = oWorkItem.GetDbConnection()
' Execute SQL and populate list...
End Using
The above code assures that your connection will be closed.
Then, turn on Option Strict and Option Explicit. This will force you to declare the Type for Description and WorkItemNumber and cast them as Strings when adding a ListItem. This will reduce run-time errors.
Finally, if this is anything but a small app you are doing as a learning experiment, you should read up on tiered application design. Your code is mixing UI, business logic, and data access in the same method. This is generally frowned upon.
Your "user interface" LoadWorkItem() method should ask a "core" method for a list of WorkItems.
Your core method should then ask a "data access" method for data.
The "data access" method should make the call to the database.
Happy coding.
Update: You can find excellent info about n-Tier architecture on MSDN. A good book to read once you grasp the fundamentals and have some confidence in .NET is Visual Basic .NET Business Objects.
Imports System.Data.SqlClient 'Reference The Sql Client
Public Class Form1
''Make sure to change the connection string below to your connection string this code only works for SQL DataBase. If Your connection String is wrong This will Not Work
Dim connString As String = "Data
Source=NameofYourSQLServer\SQLEXPRESS;Initial Catalog=NameOfYourDataBase;Integrated Security=True"
Dim tblDIV As DataTable
Dim daDIV As SqlDataAdapter
Dim dsDIV As New DataSet
Dim oCon As SqlConnection
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Dim oCon = New SqlConnection
oCon.ConnectionString = connString
dsDIV = New DataSet
' Select all Fields and order by ID or Replace * with name of Field
daDIV = New SqlDataAdapter("SELECT * FROM NameOfYourTable ORDER BY Id DESC", oCon)
'*** Define command builder to generate the necessary SQL
Dim builder As SqlCommandBuilder = New SqlCommandBuilder(daDIV)
builder.QuotePrefix = "["
builder.QuoteSuffix = "]"
Try
daDIV.FillSchema(dsDIV, SchemaType.Source, "DIV")
daDIV.Fill(dsDIV, "DIV")
tblDIV = dsDIV.Tables("DIV")
ListBox1.DataSource = tblDIV
ListBox1.DisplayMember = "NameOfTheFieldYouWanttoDisplay"
Catch ex As Exception
MsgBox("Encountered an Error;" & vbNewLine & ex.Message)
oCon.Close()
End Try
End Sub
I've tried -
DataGridView1.DataSource=Nothing
and
DataGridView1.DataSource=Nothing
DataGridView1.Refresh()
and
DataGridView1.RefreshEdit()
None of them works..
I've written a method that sets the DataSource of the DataGridView when executed. but each time i execute it, it replicates the data with new value and appends it to the previous contents of the DGV.. I wanna clear the content and then add the values.. Is that possible?
If the DataGridView is bound to any datasource, you'll have to set the DataGridView's DataSource property to Nothing.
If the DataGridView is not bound to any data source, this code will do the trick:
DataGridView.Rows.Clear()
For unbound cases note that:
DataGridView.Rows.Clear()
leaves the Columns collection in place.
DataGridView.Columns.Clear()
..will remove all the columns and rows. If you are using the DGV unbound, and on next use the columns change, clearing the Rows may not be adequate. For library code clear all the columns before adding columns.
I'd probably use this...
DataGridView1.Rows.Clear()
to clear out the rows and then rebind.
Follow the easy way like this
assume that ta is a DataTable
ta.clear()
DataGridView1.DataSource = ta
DataGridView1.DataSource = Nothing
Can you not bind the datagridview to an empty collection (instead of null). That do the trick?
To remove the old record in datagridview when you are searching for new result,with button_click event write the following code,
me.DataGridview1.DataSource.clear()
this code will help to remove the old record in datagridview.
I found that setting the datasource to null removes the columns. This is what works for me:
c#:
((DataTable)myDataGrid.DataSource).Rows.Clear();
VB:
Call CType(myDataGrid.DataSource, DataTable).Rows.Clear()
My DataGridView is also bound to a DataSource and myDataGridView.Columns.Clear() worked fine but myDataGridView.Rows.Clear() did NOT. Just an FYI for those who have tried .Rows.
Don't do anything on DataGridView, just clear the data source. I tried clearing myDataset.clear() method, then it worked.
I've got this code working in a windows form,
Public Class Form1
Private dataStuff As List(Of String)
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
DataGridView1.DataSource = Nothing
End Sub
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
dataStuff = New List(Of String)
dataStuff.Add("qwerty")
dataStuff.Add("another")
dataStuff.Add("...and another")
DataGridView1.DataSource = dataStuff
End Sub
End Class
You should remove the table from dataset if the datagrid is bind to some datatable. Your Gridview will be cleared automatically. No other way.
[YourDatasetName].Tables.Clear()
I had the same problem on gridview content clearing. The datasource i used was a datatable having no columns, and i added columns and rows programmatically to datatable. Then bind to datagridview. I tried the code related with gridview like gridView.Rows.Clear(), gridView.DataSource = Nothing
but it didn't work for me. Then try the below code related with datatable before binding it to datagridview each time.
dtStore.Rows.Clear()
dtStore.Columns.Clear()
gridView.DataSource = dtStore
And is working fine, no replication in DataGridView
1) create button named it Clear.Inside insert tfhe following code
datagridviewer.DataSource=nothing
2) In your search button begin your code by the following statement
datagridviewer.DataSource = DataSet.table
Nb:instead of table put the real name of your table
ex: datagridviewer.DataSource = DataSet.client
When feeding info from an SQL query into a datagridview you can clear the datagridview first before reloading it.
Where I have defined dbDataSet as New DataTable I can do a clear.
dbDataSet must be at the start of the form within the Public Class Form
Dim dbDataset AS New DataTable
within the code of you Private Sub, place
dbDataSet.Clear()
You may have a user scenario such that you want to keep the data binding and only temporarily clear the DataGridView. For instance, you have the user click on a facility on a map to show its attributes for editing. He is clicking for the first time, or he has already clicked on one and edited it. When the user clicks the "Select Facility" button, you would like to clear the DataGridView of the data from the previous facility (and not throw an error if it's his first selection). In this scenario, you can achieve the clean DataGridView by adapting the generated code that fills the DataGridView. Suppose the generated code looks like this:
Try
Me.Fh_maintTableAdapter.FillByHydrantNumber(Me.Fh2010DataSet.fh_maint, hydrantNum)
Catch ex As System.Exception
System.Windows.Forms.MessageBox.Show(ex.Message)
End Try
We are filling the DataGridView based on the hydrant number. Copy this code to the point where you want to clear the DataGridView and substitute a value for "hydrantNum" that you know will retrieve no data. The grid will clear. And when the user actually selects a facility (in this case, a hydrant), the binding is in place to fill the DataGridView appropriately.
If the DataGridView is bound to any datasource,
DataGridView1.DataSource = Nothing
DataGridView1.DataBind()
Dim DS As New DataSet
DS.Clear() - DATASET clear works better than DataGridView.Rows.Clear() for me :
Public Sub doQuery(sql As String)
Try
DS.Clear() '<-- here
' - CONNECT -
DBCon.Open()
' Cmd gets SQL Query
Cmd = New OleDbCommand(sql, DBCon)
DA = New OleDbDataAdapter(Cmd)
DA.Fill(DS)
' - DISCONNECT -
DBCon.Close()
Catch ex As Exception
MsgBox(ex.Message)
End Try
End Sub
If the GridView (Say the name is gvArchive) is bound to any DataSource, the following will clear it:
gvArchive.DataSource = Nothing
gvArchive.DataBind()
just write this
DataGridView1.DataSource = ""
I had the same problem: I was programmatically binding my GridView1 to one SQL table [dictonary] or another [meny] BUT when I selected the second table from my RadioButtonList1, I was getting an error (System.Web.HttpException: Field or property with the title [the first column's title from the previously selected table] was not found in the selected data source.) i.e. saying that the columns from my first-selected table couldn't be found. All I needed to do was insert:
GridView1.Columns.Clear()
before adding the table columns. Here goes the full code:
Dim connectionString As String = "your-string-details"
Dim connection As New SqlConnection(connectionString)
Then comes your first Sub:
Private Sub BindOrders()
connection.Open()
Dim sqlCommand As String = "SELECT * FROM [dictionary]"
Dim dataAdapter As New SqlDataAdapter(sqlCommand, connection)
Dim dt As New DataTable()
dataAdapter.Fill(dt)
GridView1.Columns.Clear() ' clear columns before adding new ones
If GridView1.Columns.Count <= 0 Then
Dim Field As New BoundField()
Field.DataField = "id"
Field.HeaderText = "id"
GridView1.Columns.Add(Field)
Field = New BoundField()
Field.DataField = "strArHundreds"
Field.HeaderText = "strArHundreds"
GridView1.Columns.Add(Field)
Field = New BoundField()
Field.DataField = "strArTens"
Field.HeaderText = "strArTens"
GridView1.Columns.Add(Field)
Field = New BoundField()
Field.DataField = "strArSingles"
Field.HeaderText = "strArSingles"
GridView1.Columns.Add(Field)
End If
GridView1.DataSource = dt
GridView1.DataBind()
connection.Close()
End Sub
Then comes your second Sub:
Private Sub BindDocuments()
connection.Open()
Dim sqlCommand As String = "SELECT * FROM [meny]"
Dim dataAdapter As New SqlDataAdapter(sqlCommand, connection)
Dim dt As New DataTable()
dataAdapter.Fill(dt)
GridView1.Columns.Clear() ' clear columns before adding new ones
If GridView1.Columns.Count <= 0 Then
Dim Field As New BoundField
Field = New BoundField
Field.DataField = "id"
Field.HeaderText = "id"
GridView1.Columns.Add(Field)
Field = New BoundField
Field.DataField = "nazev"
Field.HeaderText = "nazev"
GridView1.Columns.Add(Field)
End If
GridView1.DataSource = dt
GridView1.DataBind()
connection.Close()
End Sub
Finally comes your RadioButton:
Protected Sub RadioButtonList1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles RadioButtonList1.SelectedIndexChanged
Dim index As Integer
index = RadioButtonList1.SelectedIndex
Select Case index
Case 0
BindOrders()
Exit Select
Case 1
BindDocuments()
Exit Select
End Select
End Sub
For completion, here is the code for the GridView1 and the RadioButtonList1 in the associated aspx.file:
<asp:RadioButtonList ID="RadioButtonList1"
runat="server"
AutoPostBack="True"
OnSelectedIndexChanged="RadioButtonList1_SelectedIndexChanged">
<asp:ListItem>Obraty</asp:ListItem>
<asp:ListItem>Dokumenty</asp:ListItem>
</asp:RadioButtonList>
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False">
</asp:GridView>
This all works well now.
The mistake that you are making is that you seem to be using a dataset object for storing your data. Each time you use the following code to put data into your dataset you add data to the data already in your dataset.
myDataAdapter.Fill(myDataSet)
If you assign the table in your dataset to a DataGridView object in your program by the following code you will get duplicate results because you have not cleared data which is already residing in your dataset and in your dataset table.
myDataGridView.DataSource = myDataSet.Tables(0)
To avoid replicating the data you have to call clear method on your dataset object.
myDataSet.clear()
An then assign the table in your dataset to your DataGridView object.
The code is like this.
myDataSet.clear()
myDataAdapter.Fill(myDataSet)
myDataGridView.DataSource = myDataSet.Tables(0)
You can try this code:
' clear previous data
DataGridView2.DataSource = Nothing
DataGridView2.DataMember = Nothing
DataGridView2.Refresh()
Try
connection.Open()
adapter1 = New SqlDataAdapter(sql, connection)
' clear data already in the dataset
ds1.Clear()
adapter1.Fill(ds1)
DataGridView2.DataSource = ds1.Tables(0)
connection.Close()
Catch ex As Exception
MsgBox(ex.ToString)
End Try
Use this code where ever you want to implement clear datagridview command
datagridview1.datasource= nothing
datagridview1.datasource= ds
dt.clear() 'Dt as new DATATABLE
ds.clear() 'Ds as new Dataset
this code will clear the datagridview and wil stop data duplication when populating data from database.
You can do in this way:
DataGridView1.Enable = false
DataGridView1.DataSource = Nothing
DataGridView1.Enable = true
For the Clear of Grid View Data You Have to clear the dataset or Datatable
I use this Code I clear the Grid View Data even if re submit again and again it will work
Example
Dim con As New OleDbConnection
Dim cmd As New OleDbCommand
Dim da As New OleDbDataAdapter
Dim dar As OleDbDataReader
Dim dt As New DataTable
If (con.State <> 1) Then
con.Open()
End If
dt.Clear() 'To clear Data Every time to fresh data
cmd.Connection = con
cmd.CommandText = "select * from users"
da.SelectCommand = cmd
da.Fill(dt)
DataGridView1.DataSource = dt
DataGridView1.Visible = True
cmd.Dispose()
con.Close()
You can do that only by the following 2 lines:
DataGridView1.DataSource=Nothing
DataGridView1.DataBind()
You can also try this code if you want to clear all data in your DataGridView
DataGridView1.DataSource.Clear()
Try this for a specific cell:
Datagrid.Rows(RowIndex).Cells(ColIndex).Value = DBNull.Value
DgRemolques is the name of my Data grid on WPF
dgRemolques.ItemsSource = Nothing
but i need to clean also de DataTable
dtRemolques.Clear()