C# Returning Data Objects Issue

Question

I am trying to return a data object from my database so that i can access (for example) a customer ID within my ASP.NET website. Upon a customer logging in the object is returned. However, i am getting the error:

   'Invalid attempt to read when no data is present.'

I have completed an sql query on the database (Executing my stored procedure) which returns the correct information, so i know it is there. I can only presume that there is something wrong with the following method:

    using (SqlConnection sqlConn = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString))
        {
            using (SqlCommand sqlComm = new SqlCommand("Select_Customer_By_UserName_And_Password", sqlConn))
            {
                sqlComm.Connection.Open();
                try
                {
                    sqlComm.CommandType = CommandType.StoredProcedure;
                    sqlComm.Parameters.Add("@Username", SqlDbType.NVarChar, 25).Value = pUsername;
                    sqlComm.Parameters.Add("@Password", SqlDbType.NVarChar, 25).Value = pPassword;

                    using (SqlDataReader sqlDR = sqlComm.ExecuteReader(CommandBehavior.SingleRow))
                    {
                        if (sqlDR.HasRows)
                        {
                            //Creating the new object to be returned by using the data from the database.
                            return new Customer
                            {
                                CustomerID = Convert.ToInt32(sqlDR["CustomerID"])
                            };
                        }
                        else
                            return null;
                    }
                }
                catch (Exception)
                {
                    throw;
                }
                finally
                {
                    sqlComm.Connection.Close();
                }
            }
        }

Thorsten Dittmar · Accepted Answer · 2013-02-06 12:33:36Z

3

You need to call sqlDR.Read(), otherwise the "record pointer" will to point to a record. HasRows only indicates there are actually rows you can read. To read each row (or just the first one), you need to call Read once or in a while loop.

For example:

if (reader.HasRows)
{
    while (reader.Read())
        ...
}

Your code should read:

using (SqlDataReader sqlDR = sqlComm.ExecuteReader(CommandBehavior.SingleRow))
{
    if (sqlDR.Read())
    {
        //Creating the new object to be returned by using the data from the database.
        return new Customer
        {
            CustomerID = Convert.ToInt32(sqlDR["CustomerID"])
        };
    }
    else
        return null;
}

By the way: congrats on using using and parameterized queries!

answered Feb 6, 2013 at 12:33

Thorsten Dittmar

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