Question

i need to get index of a value in DataTable.

I’m trying to get like that.

 SqlDataAdapter da = new SqlDataAdapter("SELECT MessageID,SenderID,MessageContent FROM Messages WHERE ThreadID="+ThreadID, connectionString);
 //Get all messages in the Thread.
 DataTable dt = new DataTable();
 da.Fill(dt);

 da.SelectCommand.CommandText = "SELECT MessageID,SenderID,MessageContent FROM Messages WHERE MessageID="+MessageID;
 //Get the message which i need to get index.
 DataTable dtMsg = new DataTable();
 da.Fill(dtMsg);
 //Get index of dtMsg.Rows[0] in dt.
 int msgIndex = dt.Rows.IndexOf(dtMsg.Rows[0]);

I analized it when debugging values are same but its returning -1 everytime.
What i can do?

Answer 1

You are looking for a row in datatable dt when the row is actually in datatable dtMsg….

Try:

int msgIndex = dtMsg.Rows.IndexOf(dtMsg.Rows[0]);

Actually that is always going to return zero anyway as you are referencing the row by index anyway.

If what you actually want is to find a row in dt based on a value in a dtMsg row you will need to use something like Find() or Select().

Heres’s some sample code:

        // Create test data table with messageid as primary column
        DataTable dt = new DataTable();
        dt.Columns.Add("MessageID", typeof (int));
        dt.Columns.Add("SenderID", typeof(int));
        dt.Columns.Add("MessageContent", typeof(string));
        dt.PrimaryKey = new[] {dt.Columns["MessageID"]};

        // Add some data
        dt.Rows.Add(1, 10, "Message1");
        dt.Rows.Add(2, 11, "Message2");
        dt.Rows.Add(3, 12, "Message3");
        dt.Rows.Add(4, 13, "Message4");

        // Create second test data table with single row
        DataTable dtMsg = new DataTable();
        dtMsg.Columns.Add("MessageID", typeof(int));
        dtMsg.Columns.Add("SenderID", typeof(int));
        dtMsg.Columns.Add("MessageContent", typeof(string));
        dtMsg.PrimaryKey = new[] { dtMsg.Columns["MessageID"] };

        dtMsg.Rows.Add(3, 12, "Message3");

        // Not very elegant way of getting the message id from dtMsg. 
        int messageId = (int)dtMsg.Rows[0][0];

        int index = dt.Rows.IndexOf(dt.Rows.Find(messageId));

        // Result : index is 2
        Console.WriteLine(index);

This assumes that MessageId is the primary index on the table.