Question

This is probably a very simple Object Oriented Programming question. What I am trying to do is take 2 empty objects, use a query to pull data from a database, populate the empty objects with the data returned from the query, and then assert against them. See the code below:

        object test1;
        object test2;

        using (SqlConnection dbconnection = new SqlConnection(expconnstr))
        {
            dbconnection.Open();

            var expcommand = new SqlCommand(expectedquery, dbconnection);
            var actcommand = new SqlCommand(actualquery, dbconnection);

            using (SqlDataReader expreader = expcommand.ExecuteReader())
            {
                if (expreader.Read())
                {                        
                    test1 = expreader.GetValue(0);
                    expreader.Close();
                }
            }

            using (SqlDataReader actreader = actcommand.ExecuteReader())
            {
                if (actreader.Read())
                {
                    test2 = actreader.GetValue(0);
                    actreader.Close();
                }
            }
        }
        Assert.AreSame(test1, test2);

I wrote a very similar test method in VB following the same patterns and the VB code executed just fine. However whilst transitioning from VB to C#, I run into issues such as these. The compiler says “Use of unassigned variable” at the assert. However, I thought I was assigning to a value within the code block above. What am I doing wrong?

Answer 1

The possibility exists that actreader.Read() returns false, thus test2 may never get assigned and the compiler error.

You can remedy the issue by explicitly setting test1 & test2 initially to null:

object test1 = null;
object test2 = null;