I have a DataTable dt1 with columns C1(PK), C2, and C3(Unique Value) in a DataSet, on which after deleting some rows I will be doing AcceptChanges. I have another DataTable dt2 which is identical in structure to dtA. I would like to delete rows in dtA which exists in dtB compared in terms of C3(unique value) and do the AcceptChanges.
I could achieve very close, but not what I want by doing Except like below (learned from here):
var a = dt1.AsEnumerable().Select(r => r.Field<Guid>("C3"));
var b = dt2.AsEnumerable().Select(r => r.Field<Guid>("C3"));
var c = a.Except(b);
Problem with this approach is, I am getting only a list of values that belong in C3 column. I could do some more as shown here, but then again I will have a new DataTable, I wont still change the existing dt1 table.
Second approach I thought of was doing something like below:
foreach (DataRow r1 in ds1.Tables[0].Rows)
{
foreach(DataRow r2 in dt2.Rows)
{
if (r1.Field<Guid>("Guid1") == r2.Field<Guid>("Guid2"))
{
r1.Delete();
}
}
}
Here as soon as row is deleted, I get an error saying "This row has been removed from a table and does not have any data." What am I missing here?
I also have a feeling that there might be a better way of doing this, just don't know lol.
I get an error saying 'This row has been removed from a table and does not have any data' What am I missing here?
You have two loops - outer and inner. And you have two problems here. First one is deleting row when match found. On next iteration of inner loop you are trying to get value of deleted row, which throws exception. But even if you'll break inner loop after deleting row, you'll have another problem - modification of rows you are enumerating. So, your code should look like:
foreach (DataRow r1 in dt1.Rows.Cast<DataRow>().ToArray()) // save rows to array
{
foreach (DataRow r2 in dt2.Rows)
{
if (r1.Field<Guid>("C3") == r2.Field<Guid>("C3"))
{
r1.Delete();
break; // break inner loop
}
}
}
But I'd go with LINQ approach - get rows for deletion by joining rows on id field, and then delete them from table:
var rowsToDelete = from r1 in dt1.AsEnumerable()
join r2 in dt2.AsEnumerable()
on r1.Field<Guid>("C3") equals r2.Field<Guid>("C3")
select r1;
foreach(DataRow row in rowsToDelete.ToArray())
row.Delete(); // marks row as deleted;
NOTE: After you use Delete method on existing DataRow, its RowState becomes Deleted. Row remains Deleted until you call AcceptChanges, which removes row from table.
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