I have a code
foreach (DataColumn dataTableCol in this.dataTable.Columns)
{
bool columnFound = false;
foreach (GRTColumnView uiColumn in descriptor.UIColumns)
{
if (dataTableCol.ColumnName.Equals(uiColumn.Name))
{
columnFound = true;
break;
}
}
if (!columnFound)
{
if (this.dataTable.Columns.Contains(dataTableCol.ColumnName))
this.dataTable.Columns.Remove(dataTableCol.ColumnName);
}
}
I want to remove some "things" from collection if they aren't found in another collection.
When I run the above program, I get
Iteration may not execute as collection was modified
"Collection was modified" - Coz the remove must have been hit
What is the way to achieve such a thing then ?
What I can think of is make a note of all the "things" to remove and then
foreach( aThing in all_things_to_remove)
remove_from_collection(aThing)
But above doesn't seem a good way to me, as I have to do another looping and am using extra memory
In this specific case, where you're looping through a small collection containing a few columns, you can just create a new collection (via ToList()
), so that you're not iterating over the same collection you're modifying:
foreach (var dataTableCol in dataTable.Columns.Cast<DataColumn>().ToList())
{
...
dataTable.Columns.Remove(dataTableCol.ColumnName);
}
The recommended way, especially if the collection is large, is to enumerate backwards:
for (var i = dataTable.Columns.Count - 1; i >= 0; i--)
{
...
dataTable.Columns.Remove(dataTable.Columns[i].ColumnName);
}