remove null rows in data table

I have a datatable which currently contains many items which are null. A copy of this table is used as the datasource for a dropdownlist and I would like to remvoe those empty rows from the table. I though it would be simple to loop through the rows and check for null, if it's null remove it but I think it is causing a problem to alter the datatable within the for loop statement but I cannot think of any other way to do this. Please help. my code:

ipList = ds.Tables("RouterIPs").Copy


        Dim x As DataRow
        For Each x In ipList.Rows
            If x.Item("IP_Addr") Is DBNull.Value Then
                ipList.Rows.Remove(x)
            End If
        Next

the error: Collection was modified; enumeration operation may not execute. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.InvalidOperationException: Collection was modified; enumeration operation may not execute. Source Error: Line 275: ipList.Rows.Remove(x) Line 276: End If Line 277: Next Line 278: Line 279: dr = ipList.NewRow THANKS! Nic

Re: remove null rows in data table

Doing it as a regular loop and going from the end to the beginning should work.

// C# cause I don't know VB.Net
int iCount = ipList.Rows.Count;
for( int i = iCount-1; i >=0; i-- ){
     DataRow x = ipList.Rows[i];
     // check IP_Addr for nullness. If null remove it
}

You could also try removing the NULL rows in the original query. Something like:

-- Sql Server
SELECT IP_Addr  from SomeTable
WHERE IP_ADDR IS NOT NULL

You might be able to try that filter in a DataView but I'm not sure if "IS NOT NULL" is supported by the DataView's rowfilter.

Re: remove null rows in data table

Thanks for all the suggestions, McMurdoStation, I considered them all but I was also using this data for filling other thing which I would like to keep the nulls and I would to change the minimum amount of code possible so I took a different approach. Instead of removing the null rows I selectively added rows that were not null. Here is my solution:

ipList = ds.Tables("RouterIPs").Clone
        'add only non-null ip_addr dropdownlist view
        Dim i As Integer
        Dim dr As DataRow
        For i = 0 To (ds.Tables("RouterIPs").Rows.Count - 1)
            If Not ds.Tables("RouterIPs").Rows(i).Item("IP_Addr") Is DBNull.Value Then
                ipList.ImportRow(ds.Tables("RouterIPs").Rows(i))
            End If
        Next

Re: remove null rows in data table

Much more efficient would be to create a DataView for the DataTable, with the RowFilter set to "IP_Addr <> NULL". AutoFed