Gridview row.cells Unable to cast checkbox as textbox

Question

Gridview row.cells Unable to cast checkbox as textbox

Hutty 20

I have this Gridview where I'm updating a SQL table. Everything works fine until I come across a column that has checkboxes. I'm getting an error message stating unable to cast/convert checkbox to textbox. Here are the lines in question.

Dim columnValue As String = CType(row.Cells(i).Controls(0), TextBox).Text

String.Format(" WHERE {0} = '{1}'", CType(GV1.HeaderRow.Cells(1).Controls(0), LinkButton).Text, CType(row.Cells(1).Controls(0), TextBox).Text)

Thanks in advance

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Answer 1

Anonymous

Hi @Hutty , Welcome to Microsoft Q&A,

The error you're encountering is due to trying to cast a control that is not a TextBox into a TextBox. In your GridView, some cells contain CheckBox controls instead of TextBox controls. You need to check the type of control in each cell before attempting to cast it.

Dim columnValue As String

For Each cell As TableCell In row.Cells
    For Each ctrl As Control In cell.Controls
        If TypeOf ctrl Is TextBox Then
            columnValue = CType(ctrl, TextBox).Text
        ElseIf TypeOf ctrl Is CheckBox Then
            columnValue = CType(ctrl, CheckBox).Checked.ToString()
        End If
    Next
Next

Dim whereClause As String = String.Format(" WHERE {0} = '{1}'", CType(GV1.HeaderRow.Cells(1).Controls(0), LinkButton).Text, GetControlValue(row.Cells(1).Controls(0)))

Private Function GetControlValue(control As Control) As String
    If TypeOf control Is TextBox Then
        Return CType(control, TextBox).Text
    ElseIf TypeOf control Is CheckBox Then
        Return CType(control, CheckBox).Checked.ToString()
    Else
        Return String.Empty
    End If
End Function

Best Regards,

Jiale

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Hutty 20

Hi Jiale,

I believe I was able to get to the next level with your answer, as the code next error out on the cmd.ExecuteNonQuery line. However, I wasn't able to assign ColumnValue properly and insert statement was not correct. I didn't provide all the details.

The code below works, but I'm getting the error at the same place your code less the columnvalue issue, "converting data type varchar to numeric". In SQL, some fields are text and some are decimal. The gridview sees them all as text, "

columnValue = TryCast(control, TextBox).Text

" Dim columnName As String = CType(GV1.HeaderRow.Cells(i).Controls(0), LinkButton).Text
                Dim columnValue As String = String.Empty
                Dim control As Control = row.Cells(i).Controls(0)
                Select Case control.GetType().Name
                    Case "HyperLink"
                        columnValue = TryCast(control, HyperLink).Text
                        Exit Select
                    Case "TextBox"
                        columnValue = TryCast(control, TextBox).Text
                        Exit Select
                    Case "LinkButton"
                        columnValue = TryCast(control, LinkButton).Text
                        Exit Select
                    Case "CheckBox"
                        columnValue = TryCast(control, CheckBox).Checked
                        Exit Select
                End Select
                sql += String.Format("{0} = '{1}', ", columnName, columnValue)
            Next
            sql = sql.Substring(0, sql.LastIndexOf(", "))
            sql += String.Format(" WHERE {0} = '{1}'", CType(GV1.HeaderRow.Cells(1).Controls(0), LinkButton).Text, CType(row.Cells(1).Controls(0), TextBox).Text)
            Using cmd As SqlCommand = New SqlCommand(sql, con)
                con.Open()
                cmd.ExecuteNonQuery()
                con.Close()

Anonymous

Looping through rows and cells: The code loops through each row and cell in the GridView. Control type handling: Checks the type of control (HyperLink, TextBox, LinkButton, CheckBox) and retrieves the value accordingly.

' Loop through each row in the GridView
For Each row As GridViewRow In GV1.Rows
    If row.RowType = DataControlRowType.DataRow Then
        Dim sql As String = "UPDATE YourTable SET "
        For i As Integer = 0 To GV1.HeaderRow.Cells.Count - 1
            ' Get column name
            Dim columnName As String = CType(GV1.HeaderRow.Cells(i).Controls(0), LinkButton).Text
            ' Initialize column value
            Dim columnValue As String = String.Empty
            ' Get control from cell
            Dim control As Control = row.Cells(i).Controls(0)

            ' Check the type of control and get the value accordingly
            Select Case control.GetType().Name
                Case "HyperLink"
                    columnValue = TryCast(control, HyperLink).Text
                Case "TextBox"
                    columnValue = TryCast(control, TextBox).Text
                Case "LinkButton"
                    columnValue = TryCast(control, LinkButton).Text
                Case "CheckBox"
                    columnValue = CType(TryCast(control, CheckBox).Checked, Boolean).ToString()
            End Select

            ' Determine the SQL value format based on column name or data type
            Dim columnType As String = GetColumnType(columnName)
            If columnType = "nvarchar" Or columnType = "varchar" Then
                columnValue = String.Format("'{0}'", columnValue)
            ElseIf columnType = "decimal" Or columnType = "int" Then
                columnValue = String.Format("{0}", columnValue)
            End If

            ' Build SQL string
            sql += String.Format("{0} = {1}, ", columnName, columnValue)
        Next

        ' Remove the last comma and space
        sql = sql.Substring(0, sql.LastIndexOf(", "))

        ' Add WHERE clause
        sql += String.Format(" WHERE {0} = '{1}'", CType(GV1.HeaderRow.Cells(1).Controls(0), LinkButton).Text, CType(row.Cells(1).Controls(0), TextBox).Text)

        ' Execute SQL command
        Using con As New SqlConnection(connectionString)
            Using cmd As New SqlCommand(sql, con)
                con.Open()
                cmd.ExecuteNonQuery()
                con.Close()
            End Using
        End Using
    End If
Next

' Function to determine the column type based on column name
Private Function GetColumnType(columnName As String) As String
    ' You can implement a way to get the column type based on the column name
    ' This is a simplified example, adjust it based on your schema
    Select Case columnName
        Case "YourTextColumn"
            Return "nvarchar"
        Case "YourDecimalColumn"
            Return "decimal"
        Case "YourIntColumn"
            Return "int"
        Case Else
            Return "nvarchar"
    End Select
End Function

Hutty 20 Reputation points

2024-06-16T02:16:53.48+00:00

That works! Thanks Jiale.

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Gridview row.cells Unable to cast checkbox as textbox

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