Question

I want to sort a DataTable based on a column which has date value. I was running in to issues so i created following test method:

private static void Test()
    {
        DateTime testDate = DateTime.Parse("01/01/2011");

        DataTable table = new DataTable();
        table.Columns.Add("dateValue");
        table.Columns.Add("slNo");

        DataRow row1 = table.NewRow();
        row1["dateValue"] = "01/01/2011";
        row1["slNo"] = "1";

        DataRow row2 = table.NewRow();
        row2["dateValue"] = "01/02/2011";
        row2["slNo"] = "1";
        DataRow row3 = table.NewRow();
        row3["dateValue"] = "02/01/2011";
        row3["slNo"] = "1";
        DataRow row4 = table.NewRow();
        row4["dateValue"] = "01/03/2011";
        row4["slNo"] = "1";

        table.Rows.Add(row1);
        table.Rows.Add(row2);
        table.Rows.Add(row3);
        table.Rows.Add(row4);

        var t = table.AsEnumerable().OrderBy(x => x.Field<DateTime?>("dateValue")).ToList();
    }

I get Following error:

Specified cast is not valid.

The date provided can be parsed to DateTime object. But still it get the above error. Any idea what is missing?

I use C# 3.5

Answer 1

Try changing the following line:

table.Columns.Add("dateValue");

to this:

table.Columns.Add("dateValue", typeof(DateTime?));