Object reference not set to an instance of an object

.NET
1

Hello guys and good day, I need your help.

This is my net code, I’ve this error in object dr, why?
Can you help me? Thank you in advance.

    protected void BindEmployeeDetails()
    {
        myConnectionString.Open();

        httpCookie CustInfo = Request.Cookies["id"];

        SQL = "SELECT * FROM ";
        SQL = SQL + " tbl ";
        SQL = SQL + " WHERE 1 ";

        if (CustInfo != null)
        {
            SQL = SQL + " AND id = " + Request.Cookies["id"].ToString() + " ;";
        }

        OdbcCommand cmd = new OdbcCommand(SQL, myConnectionString);
        OdbcDataAdapter da = new OdbcDataAdapter(cmd);
        DataSet ds = new DataSet();
        da.Fill(ds);
        OdbcDataReader dr = null;


        if (dr.Read())
        {
            if (ds.Tables[0].Rows.Count > 0)
            {
                gvDetails.DataSource = ds;
                gvDetails.DataBind();
            }
            else
            {
                ds.Tables[0].Rows.Add(ds.Tables[0].NewRow());
                gvDetails.DataSource = ds;
                gvDetails.DataBind();
                int columncount = gvDetails.Rows[0].Cells.Count;
                gvDetails.Rows[0].Cells.Clear();
                gvDetails.Rows[0].Cells.Add(new TableCell());
                gvDetails.Rows[0].Cells[0].ColumnSpan = columncount;
                gvDetails.Rows[0].Cells[0].Text = "No record found";
            }
        }
        else
        {
            Response.Write("No user");
        }

        myConnectionString.Close();
    }


Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error:


Line 43:         OdbcDataReader dr = null;
Line 44:
Line 45:         if (dr.Read())
Line 46:         {
Line 47:             if (ds.Tables[0].Rows.Count > 0)
2

Because you set it to null…
OdbcDataReader dr = null;

You really want to use your ds variable (as that is the one you are filling).

3

thank you for suggestion, but:

Compiler Error Message: CS1061: 'System.Data.DataSet' does not contain a definition for 'Read' and no extension method 'Read' accepting a first argument of type 'System.Data.DataSet' could be found (are you missing a using directive or an assembly reference?)

Source Error:

Line 46:         if (ds.Read())
Line 47:         {
Line 48:             if (ds.Tables[0].Rows.Count > 0)
4

that would be correct, ds does not contain read. A dataset is already populated, so you simply start with your inner IF statement.

5

Ok, thank you.

But I need check that the value of the cookie is stored.

If value of the cookie is valid I show the dataset else warning user not enabled for dataset, for this use read.
Can you help me?

6

You will get an empty dataset if the value isn’t found.

think

if (ds != null && ds.Tables.Count != 0 && ds.Tables[0].Rows.Count != 0)