Winform DatagridView Numeric Column Sorting

Question

I am using just a simple DataGridView to hold a bunch of data (Funny that).

I have decimals in a particular column. But when it comes to ordering by that decimal column, it orders it incorrectly. For example :

Starting order might be :

• 0.56
• 3.45
• 500.89
• 20078.90
• 1.56
• 100.29
• 2.39

The ending order would be :

• 0.56
• 100.29
• 1.56
• 20078.90
• 2.39
• 3.45
• 500.89

As you can see, it orders it starting from the first number. And then orders it in this way.

I thought possibly I could set the column to a different "ColumnType" and that may automatically do it. But there is no "Numeric" or "Decimal" column types.

I was on MSDN looking up the issue, and I could find the "sort" method that I can use on the DataGridView. But the explanation was a bit over my head, and the examples didn't use numbers, only text so I couldnt see how I was supposed to switch things up.

Any help would be much appreciated.

Answer 1

It is sorting it by character. You need to make the column type float so it knows what comparison operator to apply.

(That is you need to make the column type in your dataset float, I believe that will work.)

Answer 2

You can solve this by adding a handler for the SortCompare event on the DataGridView with the following code:

private void dataGridView1_SortCompare(object sender, DataGridViewSortCompareEventArgs e)
{
    if (e.Column.Index == 0)
    {
        if (double.Parse(e.CellValue1.ToString()) > double.Parse(e.CellValue2.ToString()))
        {
            e.SortResult = 1;
        }
        else if (double.Parse(e.CellValue1.ToString()) < double.Parse(e.CellValue2.ToString()))
        {
            e.SortResult = -1;
        }             
        else
        {
            e.SortResult = 0;
        }
        e.Handled = true;
   }
}

From MSDN there is this description of the SortResult values:

Less than zero if the first cell will be sorted before the second cell; zero if the first cell and second cell have equivalent values; greater than zero if the second cell will be sorted before the first cell.

Note that in my test bed the only numeric column was the first (with index 0) so that is why I have the check on the column index.

Also, depending on your needs and data you may want to refine my code - for example, my code will throw an exception if for some reason you have non numeric data in your column.

You have probably seen it, but here is a link to the MSDN page on customising the DataGridView sorting. As you say, they only deal with text.