I've got a DataTable in DataSet which is filled on Form's Load event with some data from an SQL database.
I've added a Module where I am creating a function which will utilize the data from the DataTable.
Whilst I am able to get row data from Form's code, I am not able to access it from within the Module which I am guessing has something to do with references to a DataSet/DataTable.
I am typing below from top of my head...
Dim dt as Datatable
Dim dr() as Datarow
Dim DataSet1 as Dataset = New DataSet1
dt = DataSet1.comm_rates
dr = dt.select("fieldName='somevalue'")
Return a = dr(0)("fieldA")
Any help would be much appreciated.
Supposing DataSet1 is inside Class Form1, qualify your reference, e.g
Dim ds1 = Form1.DataSet1
dt = ds1.comm_rates
Related
I need to store user input (entered from the console) to a Dataset in Visual Basic. Is this possible? I can't seem to find any information online about doing so. If anyone can point me in the right direction, that would be awesome!
EDIT: The columns in my table are FirstName, LastName, State, etc. in a table named Person.
The start of the application for the console: "Enter FirstName: ", then "EnterLastName: " then etc.
The values for the user inputs are stored in there specific variables eg. firstName, lastName, so I want to know how I can put those variables in a dataset.
Thank you.
Here is a short and basic example. Most likely it will not directly work for what you need as you will probably want to use a typed dataset among other things. Since your question does not specify a question regarding the code you may have already tried, this all I am going to provide.
Option Strict On
Module Module1
Sub Main()
Dim ds As DataSet = CreateNewDataSet()
Dim entries As New List(Of String())
For i = 1 To 3
Console.WriteLine($"Enter first column value for row {i.ToString}:")
Dim input1 As String = Console.ReadLine()
Console.WriteLine($"Enter second column value for row {i.ToString}:")
Dim input2 As String = Console.ReadLine()
entries.Add({input1, input2})
Next
entries.ForEach(Sub(x) ds.Tables(0).Rows.Add(x))
End Sub
Private Function CreateNewDataSet() As DataSet
Dim ds As New DataSet()
Dim dt As New DataTable()
Dim col1 As New DataColumn("Column1")
Dim col2 As New DataColumn("Column2")
dt.Columns.AddRange({col1, col2})
ds.Tables.Add(dt)
Return ds
End Function
End Module
If you don't know column names, you can use reflection to get names of properties of input objects. You can also use attributes to filter properties. Use DataTable.LoadDataRow method to load an array as row.
here is an example to how to do it dynamically:
Dim input As New List(Of Object)
For i = 0 To 5
Console.WriteLine("enter your first name and last name:")
input.Add(New With {.First = Console.ReadLine, .Last = Console.ReadLine})
Next
Dim myData As New DataSet
Dim table = myData.Tables.Add()
table.Columns.AddRange(input.First.GetType.GetProperties.Select(Function(p) New DataColumn(p.Name)).ToArray)
input.ForEach(Function(o) table.LoadDataRow(o.GetType.GetProperties.Select(Function(p) p.GetValue(o, Nothing)).ToArray, False))
For Each row In table.Rows
Console.WriteLine("first:{0} ,Last:{1}", row(0), row(1))
Next
I know, how to increase integer, string by for statement
but I want know how to change the name by 'for ~next' statement.
For example,
Dim row_sort1 As DataTable = rows1.CopyToDataTable
Dim row_sort2 As DataTable = rows2.CopyToDataTable
Dim row_sort3 As DataTable = rows3.CopyToDataTable
Dim row_sort4 As DataTable = rows4.CopyToDataTable
Dim row_sort5 As DataTable = rows5.CopyToDataTable
Dim row_sort6 As DataTable = rows6.CopyToDataTable
Dim row_sort7 As DataTable = rows7.CopyToDataTable
I had coding like this,, bad cording So I want change by 'for ~next' statement.
I want increase the datatable name's number (1~7)
how can reflect in this coding. I want fix my coding more simple and useful.
I need your help
thank you
I assume you have a Collection of Rows which is your master where you want to copy from.
I have a similiar approach like OSKM. Better use a list collection than an array.
To access tables afterwards in the collection you can use Linq.
' Given master rowcollection
Dim masterRow As EnumerableRowCollection(Of DataRow)
' Empty table collection
Dim tableList As New List(Of DataTable)
For t As Integer = 0 To 6
' copy Master to a new table
Dim newTable As DataTable = masterRow.CopyToDataTable()
' give the new table a name
newTable.TableName = "Table" & t.ToString
' Add new table to collection
tableList.Add(newTable)
Next
' Access a certain table (i.e. Table5) using Linq
Dim table5 As DataTable = tableList.FirstOrDefault(Function(x) x.TableName = "Table5")
If i understand your question correct the following might help.
'Note your datatables will be named Datatable0 to Datatable6
Dim DTs(6) As DataTable
For i = 0 To 6
DTs(i) = New DataTable
DTs(i).TableName = "Datatable" & i
Next
There is probably better ways but this will work!
I am having trouble with a piece of sample code I am using in a Visual Basic project.
This is the sample:
Dim dataRow As DataRow
dataRow = dataSet.Tables(0).NewRow()
I am getting a NullReferenceException on the second line of the sample when I run it.
Any help is greatly appreciated!!!
The most likely explanation is that there is no table at index 0. It may also be that the datSet itself is null.
Not certain as to what the intent of the code is, but from the looks of it you are trying to add a new row to a dataset? If that is the case, you would need declare a new data row and add it to the dataset. Alternatively you should be able to add a row to the dataset and then set datarow to the new row index.
A DataSet is a collection of DataTables. I'm guessing that the DataTable reference has not yet been established and is not pointing to a DataTable object. Check whether the DataTable reference is null (Nothing in VB.NET) and if so, create a new DataTable object and add some columns to it. Then you will be able to add a new row as the DataTable reference will be pointing to a DataTable object that rows can be added to:
If IsNothing(dataset) = True Then
dataset = New DataSet
dataset.Tables.Add("Table1")
End If
If IsNothing(dataSet.Tables(0)) = True Then
dataSet.Tables(0) = New DataTable
dataSet.Tables(0).Columns.Add("FirstName", GetType(String))
dataSet.Tables(0).Columns.Add("Surname", GetType(String))
dataSet.Tables(0).Columns.Add("DateOfBirth", GetType(DateTime))
End If
Dim dataRow As DataRow = dataSet.Tables(0).NewRow
dataRow.Item("FirstName") = "John"
dataRow.Item("Surname") = "Smith"
dataRow.Item("DateOfBirth") = #11/30/1998#
dataSet.Tables(0).Rows.Add(dataRow)
I'm new to VB.net and I don't know how to display certain columns and rows in datagridview that was imported from CSV file. My problem is I have many columns and all I want to display is 2 columns:
Name,Age,Mobile Number,ID number
Alex,18,09848484841,0010
George,19,02987654321,0020
Toni,17,09277470257,0030
How can I display only the Name & Age columns and its rows?
If you use a datatable you get the data structure and collection together. something like this:
Dim sr As New IO.StreamReader(filename)
Dim dt As New DataTable
Dim newline() As String = sr.ReadLine.Split(","c)
dt.Columns.AddRange({New DataColumn(newline(0)), _
New DataColumn(newline(1))})
While (Not sr.EndOfStream)
newline = sr.ReadLine.Split(","c)
Dim newrow As DataRow = dt.NewRow
newrow.ItemArray = {newline(0), newline(1)}
dt.Rows.Add(newrow)
End While
DataGridView1.DataSource = dt
Use a custom class with properties that match the data you want to store and make an instance of that class for each row of data use read, then have a List(Of {custom class}) to hold each object and the DGV's DataSource property can view the collection in the grid. The property names in the class will be used as the header.
I am adding a tab page and datagridview to a Tab Control for every record in a datatable.
I would like to have a new Tab/DataGridView for each record (there will be ~3 for right now). I am declaring a new DataGridView D. How do I refer to these controls later?
I will want to do things like save changes in the datagridview to the database. Currently I can get the data on the screen and it looks good, but I believe I am not adding the DataGridView controls correctly because I keep re-using "D" as the control.
Dim dt As New DataTable
GetDataTable("SELECT * FROM aFeeTypes DescSeq", dt)
Dim i As Integer
'for each class in the datatable add a tab and a datagridview
For i = 0 To dt.Rows.Count - 1
Dim dr As DataRow
dr = dt.Rows(i)
Dim D = New DataGridView
D.Visible = True
Dim tp As New TabPage
tp.Name = "tp" & i
tp.Text = dr.Item("Desc2")
frmUI.tcFee.TabPages.Add(tp)
frmUI.tcFee.TabPages(i).Controls.Add(D)
dgv_Fill(D, "SELECT * FROM Fee WHERE ClassID=" & dr.Item("ClassID") & " ORDER BY Seq")
D.AutoResizeColumns()
D.Width = tp.Width
D.Height = tp.Height
Next i
this does not work:
With frmUI.Controls("D" & i)
.AutoResizeColumns()
.Width = tp.Width
.Height = tp.Height
End With
D is purely the variable name in the scope you are using it in.
You need to give the control a unique Name that yo can reference it by later.
The Name property can be used at run time to evaluate the object by
name rather than type and programmatic name. Because the Name property
returns a String type, it can be evaluated in case-style logic
statements (Select statement in Visual Basic, switch statement in
Visual C# and Visual C++).
I found a solution to the problem. The problem is that the new row has an autonumber ID.
When da.update(dt) occurs, the new row is inserted to the database. The database knows the new autonumber ID. However, the datatable does not.
For the datatable to know, the dataadapter is refilled. However, this causes the datatable to have all the old rows plus all the new rows and they all appear in the datagridview.
By clearing the old rows from the datatable, the fill refreshes all the data in the datatable and therefore refreshes the datagridview.
Public Sub dgv_AddRow(ByVal dgvName As String)
Dim dgv As DataGridView = colDataGridView.Item(dgvName)
Dim da As SqlDataAdapter = colDataAdapter.Item(dgvName)
Dim dr As DataRow = frmUI.allDataSet.Tables(dgvName).NewRow
'autopopulate the class id
dr("ClassID") = dgv.Parent.Tag
'add the new row
frmUI.allDataSet.Tables(dgvName).Rows.Add(dr)
'get the changed table
Dim dt As DataTable = frmUI.allDataSet.Tables(dgvName)
'inserts the new row to the database. concurrency violation
'will occur because datatable does not know the new Autonumber ID for the new row.
da.Update(dt)
'remove the datatable rows so they can be replaced using the adapter fill
'if rows are not cleared, following fill causes datatable to
'have existing rows plus all the rows again due to the fill
frmUI.allDataSet.Tables(dgvName).Rows.Clear()
'refill the adapter (refill the table)
'Everything you do to the underlying dataTable
'gets displayed instantly on the datagridview
da.Fill(frmUI.allDataSet, dgvName)
End Sub