Help with "Collection was modified; enumeration operation might not execute."

Question

When I use the following code, I'm getting a "Collection was modified; enumeration operation might not execute" error. If I understand this correctly, I think it means that I can't enumerate over this datatable and delete rows from it at the same time. My question is, what else can I do to achieve the result of deleting certain rows from my datatable? Here's my code:

        // Now let's loop through the datatable and find any account with no
        // LYSMKWh value and less than 4000 KWh current usage.  We'll remove those
        // from the datatable.
        currentRow = 0;
        foreach (DataRow row in resultsDT.Rows)
        {
            if ((string)resultsDT.Rows[currentRow]["LYSMKWh"] == "0")
            {
                int intKWh = Convert.ToInt32(resultsDT.Rows[currentRow]["KWH"]);
                if (intKWh < 5000)
                {
                    resultsDT.Rows[currentRow].Delete();                        
                }
            }
            resultsDT.AcceptChanges();
            currentRow++;
        }

Answer 1

You can do one of two things:

1) You can iterate over the collection in reverse order using a for loop and remove the rows inline:

for(int i = resultsDT.Rows.Count - 1; i >= 0; i--)
{
    if ((string)resultsDT.Rows[i]["LYSMKWh"] == "0")
    {
        int intKWh = Convert.ToInt32(resultsDT.Rows[i]["KWH"]);
        if (intKWh < 5000)
        {
            resultsDT.Rows[i].Delete();                        
        }
    }
    resultsDT.AcceptChanges();
}

2) You can add the rows you want to remove to a separate collection and then remove them after you iterate over the entire original collection. This is obviously less efficient so I'm not going to worry about a sample.