I am currently working in VB.NET express for desktop, 2013. I am having a hard time binding SQL data to some datagridviews on a loop with an array. I am receiving an object null error and its because on the direct cast line its not pulling the datagridview. I have multiple datagridviews on a tab control tool, one datagridview per tab. Here is my code:
try
Dim array() As Integer = {"2", "3", "4", "7", "8", "10", "11", "12"}
For Each value As Integer In array
Dim RelativeDGV = DirectCast(Me.Controls("DataGridLine" & value), DataGridView)
Using conn1 As New SqlConnection(connstring)
conn1.Open()
Using comm1 As New SqlCommand("SELECT LineNumber FROM tableA where LineNumber = @LineNumber", conn1)
comm1.Parameters.AddWithValue("@LineNumber", value)
Dim dt As New DataTable
Dim sql As New SqlDataAdapter(comm1)
sql.Fill(dt)
RelativeDGV.DataSource = dt
End Using
conn1.Close()
End Using
Next
Catch ex As Exception
MsgBox(ex.ToString)
End Try
The error is on line
Dim RelativeDGV = DirectCast(Me.Controls("DataGridLine" & value), DataGridView)
But the null error dosen't trigger until
RelativeDGV.DataSource = dt
Try to use list of DataGridView
like this :
Try
Dim array() As DataGridView = {DataGridLine2, DataGridLine3, DataGridLine4, DataGridLine7, DataGridLine8, DataGridLine10, DataGridLine11, DataGridLine12}
For Each RelativeDGV As DataGridView In array
Dim value As Integer = Regex.Replace(RelativeDGV.Name, "[^0-9]+", String.Empty)
'or like this
'Dim value As Integer = RelativeDGV.Name.Substring(12, RelativeDGV.Name.Length - 12)
Using conn1 As New SqlConnection(connstring)
conn1.Open()
Using comm1 As New SqlCommand("SELECT LineNumber FROM tableA where LineNumber = @LineNumber", conn1)
comm1.Parameters.AddWithValue("@LineNumber", value)
Dim dt As New DataTable
Dim sql As New SqlDataAdapter(comm1)
sql.Fill(dt)
RelativeDGV.DataSource = dt
End Using
conn1.Close()
End Using
Next
Catch ex As Exception
MsgBox(ex.ToString)
End Try
If the various DGV controls are on other tabs, they wont be in Me.Controls
. Rather than fish them out and cast them, you can iterate an array of them since you know the name. You also do not need to create a new connection for each nor duplicate datatables for each:
Dim dgvCtrls As DataGridView() = {DataGridLine2, DataGridLine3, DataGridLine4}
Using conn1 As New SqlConnection(connstring)
conn1.Open()
Using comm1 As New SqlCommand("SELECT LineNumber FROM...", conn1)
' ...
dt.Load(comm1.ExecuteReader())
End Using
conn1.Close()
End Using
For Each dgv In dgvCtrls
dgv.DataSource = dt
Next
You'd only need 8 identical DataTables if you dont want each grid to automatically reflect changes made in the others. For that, use a dataset on the same connection to create the tables:
Dim SQL = "..."
Dim dgvCtrls As DataGridView() = {dgv5, dgv2, dgv3,...}
Dim ds = New DataSet
Using dbcon As New SqlConnection(SQLConnStr)
Using cmd As New SqlCommand(SQL, dbcon)
dbcon.Open()
For n As Int32 = 0 To dgvCtrls.Count - 1
ds.Load(cmd.ExecuteReader, LoadOption.OverwriteChanges, dgvCtrls(n).Name)
Next
End Using
End Using
For Each dgv In dgvCtrls
dgv.DataSource = ds.Tables(dgv.Name)
Next
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