Question

I have a method that calls a stored procedure. It uses the employee number as a parameter to retrieve the data of a particular employee and then fills the data table with the result.

protected DataTable CreateDT(string empNo)
        {
            DataTable dataTable = null;
            try
            {
                SqlCommand cmd = new SqlCommand("FIND_EMPLOYEE_BY_EMPNO", pl.ConnOpen());
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.Parameters.Add(new SqlParameter("@EMPNO", (object)empNo));
                SqlDataAdapter da = new SqlDataAdapter(pl.cmd);
                dataTable = new DataTable("dt");
                da.Fill(dt);
            }
            catch (Exception x)
            {
                MessageBox.Show(x.GetBaseException().ToString(), "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
            finally
            {
                pl.MySQLConn.Close();
            }
            return dt;
        }

What I’m trying to accomplish is convert this code to LINQ, but I don’t know how get the result and fill it to my data table. See below:

alt text http://a.imageshack.us/img706/9017/testki.jpg

protected DataTable CreateDT(string empNo)
        {
            DataTable dataTable = null;
            try
            {
                DataClasses1DataContext dataClass1 = new DataClasses1DataContext();
                // I tried to cast it to DataTable, but it doesn't work...
                dataTable = (DataTable)dataClass1.findEmployeeByID(empNo);
            }
            catch (Exception x)
            {
                MessageBox.Show(x.GetBaseException().ToString(), "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
            finally
            {
                pl.MySQLConn.Close();
            }
            return dt;
        }

Please guide me how to properly do this… Thanks in advance..

Answer 1

findEmployeeByID will most likely return IEnumerable<Employee>. Considering that you are switching to using LINQ, you should actually take advantage of strongly typed data and use it across you application. So, change the return type of CreateDT function and adjust the rest of the code accordingly(I assume that the stored procedure returns at most one result):

protected Employee CreateDT(string empNo)
    {

        try
        {
            DataClasses1DataContext dataClass1 = new DataClasses1DataContext();
            // I tried to cast it to DataTable, but it doesn't work...
            return dataClass1.findEmployeeByID(empNo).FirstOrDefault();
        }
        catch (Exception x)
        {
            MessageBox.Show(x.GetBaseException().ToString(), "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
        }
        finally
        {
           //might need to dispose the context here
        }
        return null;
    }

Usage:

 var employee = CreateDT(1234);
 //You can now access members of employee in a typesafe manner
 string name = employee.Name;

EDIT Updated code – this is how you can rewrite the old DataTable code:

 protected void RetrieveEmployee(string empNo) { 
     Employee emp = CreateDT(empNo);// <---- Here 
     txtEmployeeNo.Text = emp.EmployeeNo;
     txtLastName.Text = emp.LastName;
     //....
 }

Note the absence of array indices and late bound column specifiers – ie dt[0]["EmployeeNo"] became emp.EmployeeNo – must safer, faster and easier to read.