How do I read a particular column from database..
myConnection.Open()
Dim str As String = "SELECT fullname' FROM STUDENTS"
Dim cmd As OleDb.OleDbCommand = New OleDb.OleDbCommand(str, myConnection)
dr = cmd.ExecuteReader
Dim dt As New DataTable
dt.Load(dr)
ListBox1.DataSource = dt
myConnection.Close()
Instead of getting the actual content of the database, what I get is System.Data.DataRowView
You need to set the DisplayMember property of the ListBox to the name of the column you want displayed. If you don't do that, you will see the result of calling ToString on each item, which is why you are seeing the name of the type of the items. Note that you should set the DisplayMember before setting the DataSource.
Related
i have a listbox that users can add Countries Names into it anytime.
now i need to only add new data to check if the data is new then insert it to sql.
my code not work:
For Each i As String In listbox1.Items
Dim sql = "select * From Countries where CountryName=N'" & i & "'"
Dim adp As New SqlClient.SqlDataAdapter(sql, SQlconn)
Dim ds As New DataSet
adp.Fill(ds)
Dim dt = ds.Tables(0)
If dt.Rows.Count = 0 Then
Dim dr = dt.NewRow
dr!CountryName = i
dt.Rows.Add(dr)
Dim cmd As New SqlClient.SqlCommandBuilder(adp)
adp.Update(dt)
End If
Next
If you're loading the existing names from the database in the first place then there's no need for you to check anything. Simply query the database to populate a DataTable and bind that to the ListBox. When the user adds a new country, add it to the DataTable and it will automatically show up in the ListBox. When it's time to save, just use the same data adapter to save the DataTable and only the new records will be saved.
I have the following code to populate a DataGridView component.
It works fine, but column names are defined in the DataGridView and I got a duplicated set of columns, the ones coming from the original definition and the ones coming from the dataTable. So it seems that load is not making any effort to match names between DataGridView and DataTable (I carefully set them equal).
Private Sub PopulateTable()
Dim dataConnection As New MySqlConnection
Dim cmd As New MySqlCommand
Dim reader As MySqlDataReader
Dim dataTable As New DataTable
dataConnection.ConnectionString = "server=127.0.0.1;uid=user;pwd=password;database=test"
dataConnection.Open()
' Open connection and execute query
cmd.Connection = dataConnection
cmd.CommandText = "SELECT name, type, street1, street2 FROM customer;"
' Load DataTable through reader
reader = cmd.ExecuteReader
dataTable.Load(reader)
reader.Close()
' Assign DataTable to DataGridView
dataGridView.DataSource = dataTable
' Close DB connection
dataConnection.Close()
End Sub
Is it possible to match columns from DataTable to DataGridView?
I am using sqlite database and using vb.net i am trying to print some rows in datagridview. I use the following code:
Public Sub LoadUsername()
Dim ConnectionString As String = "Data Source=info.sqlite"
Dim nSQL As String = "SELECT Name From employee"
Dim dt As DataTable = Nothing
Dim ds As New DataSet
Try
Using con As New SQLiteConnection(ConnectionString)
Using cmd As New SQLiteCommand(nSQL, con)
con.Open()
Using da As New SQLiteDataAdapter(cmd)
Console.WriteLine(da)
da.Fill(ds)
dt = ds.Tables(0)
End Using
End Using
End Using
ListBox1.ValueMember = "Name"
ListBox1.DisplayMember = "FullName"
ListBox1.DataSource = dt
Catch ex As Exception
MsgBox(ex.Message)
End Try
End Sub
but when i execute or compile this program, it shows me System.Data.DataRowView in the field where name should be. please check the image. Thanks!
There is no FullName column in your datatable yet that's what you're trying to bind the display to. Change the DisplayMember to Name as it should work correctly.
System.Data.DataRow is just the default ToString implementation as it cant find your fullname property.
I would like to do a populate a column in my listbox for each field in my Access Database.
Right now I have to manually add the field:
QUERBOX.Columns.Add("Requestor Name", 200, HorizontalAlignment.Left)
How can I adapt my code below to automatically add columns each time I run the sub?
Dim queryString As String = "SELECT * FROM Table1;"
Dim connection As OleDbConnection
Dim command As OleDbCommand
Dim data_reader As OleDbDataReader
querbox.clear
connection = New OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|\apt.accdb")
connection.Open()
command = New OleDbCommand(queryString, connection)
data_reader = Command.ExecuteReader
If data_reader.HasRows Then
While data_reader.Read
Dim newitem As New ListViewItem()
newitem.Text = data_reader.GetValue(0) 'first column
newitem.SubItems.Add(data_reader.GetValue(1)) 'second column
QUERBOX.Items.Add(newitem)
End While
End If
As Plutonix suggested in comments, a DataGridView would probably be best suited, but for the sake of answering the question here's how I've done something similar:
connection.Open()
'' Fill a DataTable with all of the Column schema for the given table of 'Table1'
Dim schemaTable As DataTable = connection.GetSchema("Columns", New String() {Nothing, Nothing, "Table1", Nothing})
'' Iterate through each column in the Schema Table
For i = 0 To schemaTable.Rows.Count - 1 Step 1
'' Declare a new item for the list
Dim newItem As New ListViewItem()
newItem.Text = schemaTable.Rows(i)!COLUMN_NAME.ToString()
newItem.SubItems.Add(schemaTable.Rows(i)!COLUMN_NAME.ToString()
'' Add new item to the interface
QUERBOX.Items.Add(newItem)
Next
connection.Close()
This has helped me in projects where the user is familiar with the database structure and may need to select the fieldname as part of the business logic. For example, allowing someone with little database knowledge to standardize the records within a given field.
I am accessing data from Access MDB file using my application developed in VB .net 2010.
I want to get values from a particular table-column to be populated in a Combo Box dropdown.
I followed a similar thread # C# Adding data to combo-box from MS Access table but as the code is in C#, I was not able to successfully implement it. And reverted back to my previous code.
Because the Table will be updated by another application as well, every time I use my utility I need to get the latest data from that table. Hence I would like to have a feature that could get all available id from table.
Below is what I have been trying to do..
'below declared at class level.
' Dim cnnOLEDB As New OleDbConnection
' Dim cmdOLEDB As New OleDbCommand
cnnOLEDB.Open()
cmdOLEDB.CommandText = "select unique_id from tag_data"
cmdOLEDB.Connection = cnnOLEDB
Dim rdrOLEDB2 As OleDbDataReader = cmdOLEDB.ExecuteReader
If rdrOLEDB2.Read = True Then
TagComboBox1.DataSource = rdrOLEDB2.Item(0).ToString
TagComboBox1.ValueMember = "unique_id"
TagComboBox1.DisplayMember = "unique_id"
End If
rdrOLEDB2.Dispose()
rdrOLEDB2.Close()
cnnOLEDB.Close()
I would recommend filling a DataTable with your query. Then you can set the DataSource of the combobox, ValueMember & the DisplayMember.
Dim dt As New DataTable
Dim query As String = "select unique_id from tag_data"
Using connection As New OleDbConnection("your connection string")
Using command As New OleDbCommand(query, connection)
Using adapter As New OleDbDataAdapter(command)
connection.Open()
adapter.Fill(dt)
connection.Close()
End Using
End Using
End Using
If dt.Rows.Count > 0 Then
TagComboBox1.DataSource = dt
TagComboBox1.ValueMember = "unique_id"
TagComboBox1.DisplayMember = "unique_id"
End If