Safely Removing DataRow In ForEach

Question

I don't understand why this code does not work.

foreach (DataRow dataRow in dataTable.Rows)
{
    if (true)
    {
        dataRow.Delete();
    }
}

Answer 1

Use this:

for (int i = 0; i < myDataTable.Rows.Count; i++)

{

 myDataTable[i].Delete();

}

Answer 2

foreach (DataRow dataRow in dataTable.Rows)
{
    if (true)
    {
        dataRow.Delete();
    }
}

dataTable.AcceptChanges();

Please Refer the snaps to understatnd the working of it.

1. Just Deleted but not removed from the DataTable.

2. Break point before AcceptChanges() Function.
3. After Eexecuting AcceptChanges() Function.

I Hope this issue resolved now.

Answer 3

You cannot modify a collection while you're iterating on it using a foreach statement.

you can try something like that :

List<DataRow> deletedRows = new List<DataRow>();

foreach (DataRow dataRow in dataTable.Rows)
{
    if(true) deletedRows.Add(dataRow);
}

foreach(DataRow dataRow in deletedRows)
{
    dataRow.Delete();
}

Answer 4

Where items have a Count, this is what I have done:

int Count = myTable.Rows.Count;

while (Count > 0) // replace condition with myTable.Rows.Count if unconditionally performed on all rows
{
    DataRow row = myTable.Rows[0] // or however you want to find your index

    // do some work
    myTable.Rows.Remove(row);

    // if you want to perform a check to break out of while
    if (someCondition)
        Count = 0;
    else
        Count = myTable.Rows.Count;
}

Note, that where objects have a .GetXXXX() collection, like FileInfo (IIRC), deleting item contents in a foreach is acceptable. One solution I have considered is creating an extension method that provides a .GetItems() method.

Answer 5

If you call the delete method you just have to call AcceptChanges() on the table you are modifying, after the foreach loop.

foreach (DataRow dataRow in dataTable.Rows)
{
    if (true)
    {
        dataRow.Delete();
    }
}

dataTable.AcceptChanges();

The delete method simply marks the row for deletion.

http://msdn.microsoft.com/en-us/library/system.data.datarow.delete%28v=VS.90%29.aspx

Answer 6

The Rows content changes while you are iterating if you delete one row, which renders the iteration invalid.

You can, however, copy the rows into a collection first and then iterate over the collection and delete the rows that way. This makes sure that the iteration is not interrupted by changing data to be iterated.