'<nullconstant>' is not declared

'<nullconstant>' is not declared. Null constant is no longer supported; use System.DBNull instead.

A statement uses the Null keyword, which is no longer supported in Visual Basic.

Error ID: BC30822

To correct this error

1. Use DBNull instead of Null. The following example demonstrates this.

   Sub TestDBNull()
       Dim t As DataTable
       ' Assume the DataGrid is bound to a DataTable.
       t = CType(DataGrid1.DataSource, DataTable)
       Dim r As DataRow
       r = t.Rows(datagrid1.CurrentCell.RowNumber)
       r.BeginEdit
       r(1) = System.DBNull.Value ' Assign DBNull to the record.
       r.EndEdit
       r.AcceptChanges
       If r.IsNull(1) Then
           MsgBox("")
       End If
   End Sub
   

2. Use the Nothing (Visual Basic) keyword for assignments and comparisons when you use object variables. The following example demonstrates this.

   Sub TestNothing()
       Dim cls As Object
       ' cls is Nothing if it has not been assigned using the New keyword.
       If (cls Is Nothing) Then
           MsgBox("cls is Nothing")
       End If
       cls = Nothing ' Assign Nothing to the class variable cls.
   End Sub
   

See Also

Concepts

Programming Element Support Changes Summary

Reference

DBNull

Nothing (Visual Basic)