Cast from type 'DBNull' to type 'String' is not valid

Use an if statement to check if the cell value is null before assigning it to the string

if (Not (TblWorkorderDataGridView.CurrentCell.Value is Nothing or TblWorkorderDataGridView.CurrentCell.Value = DBNull.value))
  strUpperValue = TblWorkorderDataGridView.CurrentCell.Value

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Here's another way to code it ...
 

strUpperValue = ""
If TblWorkorderDataGridView.CurrentCell.Value IsNot Nothing AndAlso TblWorkorderDataGridView.CurrentCell.Value.Length > 0 Then
    strUpperValue = TblWorkorderDataGridView.CurrentCell.Value 
End If

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Hi
I'm using following function:

        Public Shared Function GetDBString(ByVal o As Object, Optional ByVal strDBNull As String = "") As String
            If o Is Nothing Then Return strDBNull
            If IsDBNull(o) Then Return strDBNull Else Return o.ToString
        End Function

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Now you can use from anywhere:
MsgBox(GetDBString(TblWorkorderDataGridView.CurrentCell.Value,"Missing"))
'or
Dim x as String=GetDBString(TblWorkorderDataGridView.CurrentCell.Value)
If x="" Then
   MsgBox("Null value!")
End If

I tried all of the code samples above and none worked.

I get the error on this line when deleting text from a databridview cell (datatype nvarchar (3):
strUpperValue = TblBasicPlumbingWorkorderDataGridView.CurrentCell.Value


Here are the error details:
System.InvalidCastException was unhandled
  Message="Conversion from type 'DBNull' to type 'String' is not valid."
  Source="Microsoft.VisualBasic"
  StackTrace:
       at Microsoft.VisualBasic.CompilerServices.Conversions.ToString(Object Value)
       at Plumbing.frmTrackingUPBJobs.TblWorkorderDataGridView_CellEndEdit(Object sender, DataGridViewCellEventArgs e) in C:\Documents and Settings\Dave\My Documents\Visual Studio 2005\Projects\Plumbing\Plumbing\frmTrackingUPBJobs.vb:line 68
       at System.Windows.Forms.DataGridView.OnCellEndEdit(DataGridViewCellEventArgs e)
       at System.Windows.Forms.DataGridView.EndEdit(DataGridViewDataErrorContexts context, DataGridViewValidateCellInternal validateCell, Boolean fireCellLeave, Boolean fireCellEnter, Boolean fireRowLeave, Boolean fireRowEnter, Boolean fireLeave, Boolean keepFocus, Boolean resetCurrentCell, Boolean resetAnchorCell)
       at System.Windows.Forms.DataGridView.SetCurrentCellAddressCore(Int32 columnIndex, Int32 rowIndex, Boolean setAnchorCellAddress, Boolean validateCurrentCell, Boolean throughMouseClick)
       at System.Windows.Forms.DataGridView.OnCellMouseDown(HitTestInfo hti, Boolean isShiftDown, Boolean isControlDown)
       at System.Windows.Forms.DataGridView.OnCellMouseDown(DataGridViewCellMouseEventArgs e)
       at System.Windows.Forms.DataGridView.OnMouseDown(MouseEventArgs e)
       at System.Windows.Forms.Control.WmMouseDown(Message& m, MouseButtons button, Int32 clicks)
       at System.Windows.Forms.Control.WndProc(Message& m)
       at System.Windows.Forms.DataGridView.WndProc(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
       at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
       at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
       at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.Run(ApplicationContext context)
       at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.OnRun()
       at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.DoApplicationModel()
       at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.Run(String[] commandLine)
       at Plumbing.My.MyApplication.Main(String[] Args) in 17d14f5c-a337-4978-8281-53493378c1071.vb:line 81
       at System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args)
       at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()

Can someone help on this?

Thanks!

All I want to do is convert the cell value to upper case and have nothing when deleted.

If I add  a binding textbox to the form - the datagridview cell formatting works fine and deletes...

Did you try
strUpperValue = GetDBString(TblBasicPlumbingWorkorderDataGridView.CurrentCell.Value)

You just want make textbox uppercase?

    Private Sub DataGridView1_EditingControlShowing(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewEditingControlShowingEventArgs) Handles DataGridView1.EditingControlShowing
        If TypeOf e.Control Is TextBox Then
            If CType(sender, DataGridView).CurrentCell.ColumnIndex = 10 Then
                CType(e.Control, TextBox).CharacterCasing = CharacterCasing.Upper
            End If
        End If
    End Sub

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Not textbox, but datagridview column to uppercase...

the code I have is working fine...

Thanks!

I accepted my comment as a solution because no other comments worked.