Getting CHANGED value from Datagrid?

Ron Howerton · December 15th, 2003, 12:17 PM

I posted this to the beginner board last week and had lots of reads but no responses, so I thought I'd try it here this week:

I want to obtain the value entered into a datagrid cell in a VB.NET windows app (not ASP), so I can validate it before the change is applied to the dataset. The following code gets the ORIGINAL value in the cell, but I can't figure out how to obtain the NEW value:

grdServices.Item(grdServices.CurrentCell).ToString ()

What do I need to do to get the new value entered by the user? I've tried the _Validating function, which fires when the user leaves the cell (and, oddly, when the user enters another cell), but its arguments don't appear to contain any properties to obtain the NEW value, just the OLD one. Is there another method I should use or what?

Ron Howerton · December 15th, 2003, 04:54 PM

Here's the answer I've finally found, if anybody cares:

Although it seems intuitive, you CANNOT check the new value by referencing the grid. It's necessary instead to reference the underlying table in the dataset (even though the table has NOT actually been updated - it makes no sense to me, but then very little MS has done with .NET makes sense to me) using the ColumnChanging event. Here's some genericized code that works:

Private Sub ColumnChangingValidation(ByVal sender As Object, _
  ByVal e As System.Data.DataColumnChangeEventArgs)

' first check the column name because this subroutine
' is not column specific (that would be too easy)
    If (e.Column.ColumnName.Equals("Server")) Then

            ' Validate e.ProposedValue, which is
            ' what the user entered
            If YourValidationRoutine(e.ProposedValue) = False Then

                ' set the row hover message on the table that
                ' makes it magically appear on the grid
                e.Row.RowError = "The Server column contains an error"

                ' set the column hover message on the table that
                ' makes it magically appear on the grid
                e.Row.SetColumnError(e.Column, "Value cannot be " & _ CType(e.ProposedValue, String) & " - Expected blah, blah, blah...")
            End If
        End If
    End Sub

Next, the ColumnChanging event has to be related to the table in the dataset:

AddHandler DataSetName.Tables("TableName").ColumnChanging, AddressOf ColumnChangingValidation

Then when the user enters a value into the indicated column and tabs out or clicks on another cell or another control, the event fires and the error indicator appears on the grid row and column. I haven't figured out hwo to cancel the update to the field in the table yet, but it should only take me another week or so to figure out that minor detail.

If you want to know how to do this in C#, you can find MicroSoft's ever-so-helpful example code at:

http://msdn.microsoft.com/library/de...ridcontrol.asp

fluffycheeseball · July 20th, 2004, 09:08 AM

Thanks Ron. This solved my problem too.:)

fluffycheeseball

fluffycheeseball · July 20th, 2004, 10:29 AM

Has anyone else noticed a problem with ClearErrors();

I have a dateGrid with a user entry column. Different rows in this column contain strings, numbers etc. Thus I need to do some manual validation of user input.

I am using a System.Data.DataColumnChangeEventHandler (as advised by Ron) and this works fine. When the user enters an erroneous value I call e.Row.SetColumnError(e.Column, "my error string");
Result is a little exclamation mark and the error string is displayed whenever the mouse is over the cell.

But! Once the user enters a valid value I call ClearErrors(). th exclamation mark clears as expected but I cannot get rid of the error string.
Yet, if I then call e.Row.GetColumnError(e.Column) and write the result to console - it shows an empty error string!

I've tried calling e.Row.SetColumnError(e.Column, " "), before (and after ) calling Clear Errors(). No affect

Oddly enough manually resizing the window does stop the error string poopping up every time the mouse is over teh (now correct) cell. But invalidating th edatagrid, refreshing the datagrid (or its form) has no effect.

Any suggestions?

fluffycheeseball

dapanther99 · January 5th, 2005, 11:36 AM

Hi,
I am having similar issues clearing the errors in C#. Basically it appears that Microsoft made the function to create the error and to clear the whole row of errors but not a column. Does anyone else have a solution on this?

dapanther

dapanther99 · January 5th, 2005, 02:11 PM

Hi all,
I got this working this morning in C#. Basically you need to send the SetColumnError a null instead of an empty string and it removes the column error prompt. You will still need to also remove the row error prompt if the row contains no additional errors (I am checking 15 columns). In order to do this I checked the GetColumnsInError array for it's length and if it is less than 1 I kick off the ClearErrors method for the row. Below is some sample code from the hadnler I created. Note: the numTest method is just a simple method to check for numbers in strings...

Code:

        private void data_ColumnChanging(object sender, System.Data.DataColumnChangeEventArgs e) 
        {
            // validate the first column            
            if (e.Column.ColumnName.Equals("fname"))
            {
                if (numTest(e.ProposedValue.ToString()) == true)
                {
                    e.ProposedValue = "Error";
                    e.Row.RowError = "This row contains an error.";
                    e.Row.SetColumnError(e.Column, "First Name must be text.");
                }
                else 
                {
                    if (e.Row.GetColumnError(e.Column) != "")
                    {
                        e.Row.SetColumnError(e.Column, null);
                    }

                    if (e.Row.GetColumnsInError().Length < 1)
                    {
                        e.Row.ClearErrors();
                    }
                }
            }
         }