Calling Stored Procedure from C# using a backgroundworker and getting an output message (Repost for complete code)

Question

This is a repost of yesterdays question so i can show more complete code. To recap i am calling a stored procedure from inside a backgroundworker DoWork method. The stored procedure is returning raiseerrors correctly and i am displaying a progress bar. The problem i am having is the output variable from the stored Procedure never returns the message. I will show the appropriate code from the stored procedure first.

ALTER PROCEDURE [dbo].[ua_sp_PostPeriodicDues]
  @periodCode               nchar(1)
, @nextPostingDate          datetime
, @repost                   int
, @localFieldName           varchar(50)
, @userCd                   varchar(8)
, @runNow                   bit
, @returnMessage            varchar(100)    OUTPUT      

AS
BEGIN
Declare @rowsProcessed      As Integer

SET @rowsProcessed = 0

SET @returnMessage =  'Post Periodic Dues for ' + @nextPostingDate + ' successfully completed on ' + GetDate() + ' ' + @rowsProcessed + ' records were processed.'
END

Now here is the c# code that calls the stored procedure.

public class PostPeriodicDuesService
{
    private string periodCode;
    private DateTime nextPostingDate;
    private int repost;
    private string localFieldName;
    private string userCd;
    private string title;
    private BackgroundWorker bgWorker;
    private ProgressBarForm progressBarForm;
    private int runNow = 1;
    private string returnMessage = "";

    public PostPeriodicDuesService()
    {
        bgWorker = new BackgroundWorker();

        this.bgWorker.WorkerReportsProgress = true;
        this.bgWorker.WorkerSupportsCancellation = true;
        this.bgWorker.DoWork += new System.ComponentModel.DoWorkEventHandler(this.bgWorker_DoWork);
        this.bgWorker.ProgressChanged += new System.ComponentModel.ProgressChangedEventHandler(this.bgWorker_ProgressChanged);
        this.bgWorker.RunWorkerCompleted += new System.ComponentModel.RunWorkerCompletedEventHandler(this.bgWorker_RunWorkerCompleted);         
    }

    public void RunPostPeriodicDues(PostPeriodicSetting setting)
    {
        periodCode = setting.FreqCode;
        nextPostingDate = DateTime.Parse(setting.NextPostingDate1.ToString());
        repost = setting.RepostChk ? 1 : 0;
        localFieldName = setting.FldName;
        userCd = CommonUser.CurrentUser.UserCd;
        title = "Monthly";

        Program.MainForm.DisplayMessage("Processing " + title + " Post Periodic Dues....");
        Cursor.Current = Cursors.WaitCursor;

        progressBarForm = new ProgressBarForm("Running Post Periodic Dues", 0);
        progressBarForm.Show();

        bgWorker.RunWorkerAsync();
    }

    private void bgWorker_DoWork(object sender, DoWorkEventArgs e)
    {
        var self = (BackgroundWorker)sender;

        var connection = ConnectionStringBuilder.GetSqlConnectionString();

        SqlConnection conn = new SqlConnection(connection);
        conn.FireInfoMessageEventOnUserErrors = true;
        conn.Open();
        conn.InfoMessage += (o, args) => self.ReportProgress(0, args.Message);

        SqlCommand cmd = new SqlCommand("ua_sp_PostPeriodicDues", conn);
        cmd.CommandType = CommandType.StoredProcedure;
        cmd.CommandTimeout = 0;
        cmd.Parameters.Add(new SqlParameter("@periodCode", periodCode));
        cmd.Parameters.Add(new SqlParameter("@nextPostingDate", nextPostingDate));
        cmd.Parameters.Add(new SqlParameter("@repost", repost));
        cmd.Parameters.Add(new SqlParameter("@localFieldName", localFieldName));
        cmd.Parameters.Add(new SqlParameter("@userCd", userCd));
        cmd.Parameters.Add(new SqlParameter("@runNow", runNow));
        SqlParameter returnParam = new SqlParameter("@returnMessage", SqlDbType.VarChar, 100);
        returnParam.Direction = ParameterDirection.Output;
        cmd.Parameters.Add(returnParam);

        cmd.ExecuteNonQuery();
        returnMessage = returnParam.Value.ToString();

        conn.Close();
    }

    private void bgWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
    {
        var message = Convert.ToString(e.UserState);

        if (message.StartsWith("Deleting"))
        {
            progressBarForm.SetMessageLabel(message);
        }

        if (message.StartsWith("Running"))
        {
            progressBarForm.SetMessageLabel(message);
        }

        if (message.EndsWith(" Total Rows"))
        {
            int totalRows;
            if (int.TryParse(message.Split(' ')[0], out totalRows))
                progressBarForm.SetTotalRows(totalRows);
        } 

        if (message.EndsWith(" Rows Processed"))
        {
            int rowsProcessed;
            if (int.TryParse(message.Split(' ')[0], out rowsProcessed))
                progressBarForm.IncrementProgressBar(rowsProcessed);
        }
    }

    private void bgWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        progressBarForm.Kill();
        Cursor.Current = Cursors.Default;
        MessageBox.Show(returnMessage);           
        Program.MainForm.DisplayMessage("Ready...");
    }
}

When i display the returnMessage using MessageBox.Show, the value is empty. The output parameter is not returned from the stored procedure. What I am doing wrong here?

Answer 1

I suspect @returnMessage is never actually set to the string you are expecting because you are concatenating character data with a date and an integer without any conversions. This is probably actually throwing a SqlException as well, and the BackgroundWorker is likely obfuscating it. (Try checking e.Error in your RunWorkerCompleted handler.)

Try:

SET @returnMessage =  'Post Periodic Dues for ' + 
                       CONVERT(VARCHAR(10), @nextPostingDate, 101) + 
                       ' successfully completed on ' + 
                       CONVERT(VARCHAR(10), GETDATE(), 101) + 
                       ' ' + 
                       CAST(@rowsProcessed AS VARCHAR(16)) + 
                       ' records were processed.';