以编程方式将新行添加到 DataTable C#

Question

I have a DataTable which I fill from a database and the in code behind I am trying to add 3 more rows after each row. Below is the code. But at the 6th line I get

Exception of type 'System.OutOfMemoryException' was thrown.

  for (int i = 0; i < AlldaysList.Rows.Count; i++)
    {
        DataRow row;
        row = AlldaysList.NewRow();
        DataRow row1;
        row1 = AlldaysList.NewRow();
        DataRow row2;
        row2 = AlldaysList.NewRow();

        // Then add the new row to the collection.
        row["scenarionid"] = DBNull.Value;
        row["description"] = "";
        row1["scenarionid"] = DBNull.Value;
        row1["description"] = "";
        row2["scenarionid"] = DBNull.Value;
        row2["description"] = "";
        AlldaysList.Rows.InsertAt(row, i + 1);
        AlldaysList.Rows.InsertAt(row1, i + 2);
        AlldaysList.Rows.InsertAt(row2, i + 3);
        i++;
    }

Answer 1

//This could be the problem
i < AlldaysList.Rows.Count

i think u should have a variable called int rowCount = AlldaysList.Rows.Count; before the loop..

the loop should be  for (int i = 0; i < rowCount; i++)

The reason why i say this is because if u add 3 rows inside the loop ur AlldaysList.Rows.Count is changing by +3 and ur targeting a dynamic variable instead of a static one and so it goes into the loop again and causes an exception..

Answer 2

I think you should do something like this:

int origRowCount = AlldaysList.Rows.Count;
for (int i = 0; i < origRowCount; i++)
{
    for (int j = 1; j <= 3; j++)
    {
        AlldaysList.Rows.InsertAt(MakeNewAlldaysRow(AlldaysList), i * 4 + j);
    }
}

// ....
// (separate method)
static DataRow MakeNewAlldaysRow(DataTable table)
{
    DataRow row = table.NewRow();
    row["scenarionid"] = DBNull.Value;
    row["description"] = "";

    return row;
}

Since the list of rows is going to be increasing, you need to make a note of the row count before you start adding rows. Also, the insert locations are going to be increasing by 4 , hence i * 4 + j .

Answer 3

Generalised version of your code, you can add any number of rows by just changing the value of variable RowsToAdd. You dn't need crate three DataRow variable(row,row1,row2)...

int RowsToAdd=3
int rowCount = AlldaysList.Rows.Count;
for (int i = 0; i < rowCount; i++)
{
   for (int j = 0; j < RowsToAdd; j++)
   {
     DataRow dr = AlldaysList.NewRow();
     dr["scenarionid"] = DBNull.Value;
     dr["description"] = "";

     AlldaysList.Rows.Add(dr);
   }
}