I created a DataSet fro a query and populate a table with its values. But when a field contains NULL value I receive an error message about conversion DBNull data type to string. Can anyone help me how to solve this problem?
The code as follows:

ByVal strTableName As String)
Dim r As TableRow
Dim c As TableCell
Dim myTable As DataTable
Dim myRow As DataRow
Dim myColumn As DataColumn
Dim strTemp As String

' For each table in the DataSet, print the row values.
myTable = myDataSet.Tables(strTableName)

For Each myRow In myTable.Rows
r = New TableRow()

For Each myColumn In myTable.Columns
c = New TableCell()

strTemp = myRow(myColumn)

c.Controls.Add(New LiteralControl(strTemp))
r.Cells.Add(c)

Next myColumn

Table1.Rows.Add(r)
Next myRow

End Sub