dtatgridview is not clearing up? - vb.net

Question

I have searched all through the web and still cannot find the right way to clear up my datagidview for the update. It maybe because I put two datagrid view in one windows form, I don't know. Though it worked, I mean it cleared up the datasource, before I added the new datagridview.
Can anyone please help me find the solution to refresh the datagridview? I also did used the datagridview.datasource.refresh(). But it still the same?
Any Help or lead to the solution is very much appreciated, Thanks.
my code to clear the datagridview is :
least30.DataSource = Nothing
least30.CancelEdit()
least30.EndEdit()
least30.Columns.Clear()
least30.Rows.Clear()
mysqlcon.ConnectionString = "server =" + srvr + ";" + "user id =" + usrnm + ";" + "password =" + pswd + ";" + "database =" + dtb
mysqlcon.Open()
mysqlcmd.Connection = mysqlcon
mysqlcmd.CommandText = "select " & "itm" & ", sum( " & "count" & " ) from " & "dtb.tbl" & " group by " & "itm" & " order by sum( " & "count" & " ) asc limit 40"
mysqlrd = mysqlcmd.ExecuteReader
mysqldt.Load(mysqlrd)
least30.DataSource = mysqldt
mysqlrd.Close()
mysqlcon.Close()
End Sub

Answer 1

You should be using a data adapter. You call Fill on the data adapter to populate a DataTable and you bind that to the grid, preferably via a BindingSource. The user makes all the changes they want via the grid. You then call EndEdit on the BindingSource to ensure that any pending change is committed and then Update on the data adapter to save the changes from the DataTable back to the database. Obviously you need to populate the InsertCommand, UpdateCommand and DeleteCommand of the data adapter to save changes of those types.
Here's a quick example:
Private adapter As SqlDataAdapter
Private table As DataTable
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Dim builder As New SqlConnectionStringBuilder With
{
.DataSource = "MachineName\InstanceName",
.InitialCatalog = "DatabaseName",
.IntegratedSecurity = True
}
Dim connection As New SqlConnection(builder.ConnectionString)
Dim insertCommand As New SqlCommand("INSERT INTO SomeTable (SomeColumn) VALUES #SomeColumn", connection)
Dim updateCommand As New SqlCommand("UPDATE SomeTable SET SomeColumn = #SomeColumn WHERE Id = #Id", connection)
Dim deleteCommand As New SqlCommand("DELETE SomeTable WHERE Id = #Id", connection)
insertCommand.Parameters.Add("#SomeColumn", SqlDbType.VarChar, 50, "SomeColumn")
updateCommand.Parameters.Add("#SomeColumn", SqlDbType.VarChar, 50, "SomeColumn")
updateCommand.Parameters.Add("#Id", SqlDbType.Int, 0, "Id")
deleteCommand.Parameters.Add("#Id", SqlDbType.Int, 0, "Id")
adapter = New SqlDataAdapter("SELECT * FROM SomeTable", connection) With
{
.InsertCommand = insertCommand,
.UpdateCommand = updateCommand,
.DeleteCommand = deleteCommand
}
table = New DataTable
adapter.Fill(table)
BindingSource1.DataSource = table
DataGridView1.DataSource = BindingSource1
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Validate()
BindingSource1.EndEdit()
adapter.Update(table)
End Sub
That code is written for SQL Server but it will be almost identical for MySQL. Just change all the System.Data.SqlClient types to the corresponding MySql.Data.MySqlClient types, e.g. SqlConnection to MySqlConnection. You would have to make some minor adjustments to the construction of the connection string and you'll need to change the SQL code and parameters to match your data but the principles all remain exactly the same.