Question

I built a console application and I’m trying to test if my application works as expected.
I create an instance of the API class as shown in the code below but I receive an error:
An object reference is required for the non-static field. I’ve already checked similar issues like this one but it seems different. What am I doing wrong?

namespace ConsoleApplication1
{
    class Api
    {

        String ConStr = "SERVER=myservername; Database=mydb; UID=mylogin; PWD=mypassword;encrypt=no;enlist=false";
        String bin_Num = "201284-11-000";
        Label lblResults;

        static void Main(string[] args)
        {
            Api Test_api = new Api();
            Test_api.getQualWeight(ConStr, bin_Num, lblResults);
        }

        public Dictionary<String, String> getQualWeight(String sqlConStr, String inBin, Label lblResults)
        {
            Dictionary<String, String> qualList = new Dictionary<string, string>();
            string selectSQL = "select Name,qual_weight from Qualification_type "
                             + "where ID in (select Qualification_ID from Qualifications where BIN = @inBin)";
            con = getConn(sqlConStr);
            SqlCommand cmd = new SqlCommand(selectSQL, con);
            cmd.Parameters.AddWithValue("@inBin", inBin);
            SqlDataReader reader;

            try
            {
                con.Open();
                reader = cmd.ExecuteReader();
                while (reader.Read())
                {
                    qualList.Add(reader[0].ToString(), reader[1].ToString());
                }
                reader.Close();
                return qualList;
            }
            catch (Exception err)
            {
                lblResults.Text = "error fetching qualification weight " + err.Message;
                return null;
            }
            finally
            {
                con.Close();
            }
        }
    }
}

Answer 1

If you want to use an Object and not have all the members be static you need to reference the non-static member variables using an instance of the class.

Change:

Test_api.getQualWeight(ConStr, bin_Num, lblResults);

To:

Test_api.getQualWeight(Test_api.ConStr, Test_api.bin_Num, Test_api.lblResults);

Because ConStr, bin_Num, and lblResults are instance variables they must be references with an instance of the class – in this case Test_api.

Alternately, you could move those values into a global, static, scope by changing their declarations from:

String ConStr = "SERVER=myservername; Database=mydb; UID=mylogin; PWD=mypassword;encrypt=no;enlist=false";
String bin_Num = "201284-11-000";
Label lblResults;

To this:

static String ConStr = "SERVER=myservername; Database=mydb; UID=mylogin; PWD=mypassword;encrypt=no;enlist=false";
static String bin_Num = "201284-11-000";
static Label lblResults;