Question

I have 2 data tables, one in which i have my data(D1) with a unique data Id and in another data table(D2) i have the Ids of all the records of my data table(D1) in a particular order.How can i sort my data table(D1) based on the order of Ids in D2.I am using c# asp.net

Answer 1

You could copy the rows in the ordering table into a Dicationary with an index. Assuming your key field is named Key the code might look like this:

static void Main(string[] args)
{
    var dt = new DataTable("Data");
    var dtOrder = new DataTable("Order");

    // Insert some data here

    int i = 0;
    var orderDict = new Dictionary<object, int>();
    foreach(DataRow row in dtOrder.Rows)
    {
        orderDict.Add(row["Key"], ++i);
    }

    var ordered = dt.Rows.Cast<DataRow>().OrderBy(r => orderDict[r["Key"]]);
}

As I read Peaceman71’s comment, I think it is worth mentioning that this is a disconnected approach. Any proper database software will do this for you as well.