locked
Interesting problem with getting OUTPUT parameters from SQL Server using C# RRS feed

  • Question

  • User830836415 posted

     I have the following SP:

     

    Create procedure dbo.example

    (

    @test INT OUTPUT

    )

    AS

    BEGIN

    SET @test = 5

    SELECT * from Users

    END

    GO

     

     

    and when I try calling it from C# using an SqlCommand with adding an output parameter and getting it's value, I get that the value is NULL. (I should mention that I use ExecuteReader)

    However,  if I alter the SP and remove the select line, the c# code works and returns the value 5.

     

    Monday, January 21, 2008 6:46 AM

Answers

All replies

  • User1790239879 posted

    try to use return @test

    Monday, January 21, 2008 9:32 AM
  • User-1630358218 posted

    try to use return @test

     

     
    I am having the exact same problem. This reply is not helpful because the stored procedure may have multiple output parameters. When using return, you will only be able to return one value.

    EDIT: To clarify my problem, and to contradict the original post, the value of that output parameter is not NULL (DbNull.Value), it's null (good old-fashioned C# null). Which implies that the framework is not assigning any value at all to the output parameter after execution of the command. Actually, when I set a value to the parameter before executing the command, it gets replaced with null after execution. That's even more strange.

    More Info:

    If I execute the stored proc in Visual Studio and examine the results in the output window, it behaves exactly as expected. I see my query results, the value of my output parameter, and a @RETURN_VALUE of zero (the default if you don't use a RETURN statement)

    If I don't assign to the output parameter (which I named @ReturnCode) in the proc then I get <NULL> in the window. So, again, it's working exactly as expected when executing in VS. It seems that the SqlClient library is to blame.

    With SELECT and setting the output param:

    MacAddress  
    ------------
    0002680117E7
    No rows affected.
    (1 row(s) returned)
    @ReturnCode = 0
    @RETURN_VALUE = 0

     
    With SELECT and not setting output param:

    MacAddress  
    ------------
    0002680117E7
    No rows affected.
    (1 row(s) returned)
    @ReturnCode = <NULL>
    @RETURN_VALUE = 0
     

    From these results it's clear that it is being set when I set it to zero in the proc (Or returned as NULL if I don't set it), but it's always null when the SqlClient framework finishes executing it.

    Wednesday, April 30, 2008 4:46 PM
  • User-1846563363 posted

    Hi

    After declaring variables Execute your command  

    db.ExecuteNonQuery(dbCommandWrapper);

    object objRetTest;

    objRetTest= db.GetParameterValue(dbCommandWrapper, "Your variable name that u passes ");

     

    if (objRetTest== DBNull.Value) return -1;

    else

    // return output parameter values

     

    Friday, May 16, 2008 7:59 AM
  • User-1088418215 posted

     I'm bumping a one year old thread:

     As anyone ever fixed this issue? I'm currently having the same exact problem and there's no solution in the thread.

    Tuesday, June 9, 2009 2:43 PM
  • User-1496008506 posted

     I too am having the same problem.  Has anyone found a solution?

    Friday, July 24, 2009 2:05 PM
  • User-1630358218 posted

    There's a simple but ugly workaround. Rather than use output parameters, select a second result set that contains one row with one column for each output variable you need. You will then have two result sets.

    SELECT * FROM SomeTable --This is your normal select result

    SELECT @Foo AS Foo, @Bar AS Bar, @Zap AS Zap --These are your "output parameters"

    Of course, you would remove the actual output parameters from the stored procedure if doing this, and just use local variables.

    If using a SqlDataReader you can use the NextResult() method to move to the next result. If using a SqlDataAdapter with a DataSet, you should get a second DataTable.

    Friday, July 24, 2009 2:18 PM
  • User-607926186 posted

    As anyone ever fixed this issue? I'm currently having the same exact problem and there's no solution in the thread.
     

     

    Try the ZipZango Database Library. ( www.zipzango.com ) I wrote it after continually running into the same type of issue. Download the demo. If you think it will work for you, drop me an email and I'll arrange to get you a full copy for free.

    Regards,

    -DG

    Tuesday, August 11, 2009 9:57 PM
  • User1829300250 posted

    Since row sets will be returned before all output parameters for a stored procedure. I guess that you will need to either retrieve or skip all row sets and then getting the output parameters. 

    Tuesday, October 27, 2009 7:23 PM
  • User-1225724552 posted

    Replace this (SET @test = 5) with select @test=5


    Sunday, November 1, 2009 5:48 AM
  • User-2076117251 posted

    i had the same problem and i just got it fixed (im not sure if this will work for evreone)

    all i did was to use the reader to the end and to close the conectien before i tryd to get the value of my output parameter:

    command.CommandType = CommandType.StoredProcedure;
    command.CommandText = "ProcName";
    
    command.Parameters.Clear();
    
    command.Parameters.AddWithValue("@inputParameter", methodArgument);
    command.Parameters.Add("@outputParameter", SqlDbType.DateTime);
    command.Parameters["@outputParameter"].Direction = ParameterDirection.Output;
    
    dbConnection.Open();
    SqlDataReader reader = command.ExecuteReader();
    
    while (reader.Read())
    {
         //do watever
    }
    connection.Close();
    
    DateTime output = (DateTime)command.Parameters["@outputParameter"].Value;

     

    Saturday, December 12, 2009 7:57 PM
  • User-2109426844 posted

    I think the problem is that your query type needs to be ExecuteScalar, not ExecuteReader.


    Have a look at this article which explains a similar scenario

    Getting the identity of a row inserted into a database table with SCOPE_IDENTITY

    Saturday, December 12, 2009 10:53 PM
  • User-1630358218 posted

    i had the same problem and i just got it fixed (im not sure if this will work for evreone)

    all i did was to use the reader to the end and to close the conectien before i tryd to get the value of my output parameter:

    Fascinating! That worked for me, too.


    It turns out that I was wrong in my original post, or something changed. When I tested this just now, the value of the parameter before closing the connection was DbNull, and not a .Net null.

    Wednesday, January 6, 2010 3:59 PM
  • User-141307173 posted

    I had the same problem as the first person in the thread (a sproc with a result set and one or more output params), and my solution was the same as for kvikasilfur

    • Using ExecuteReader(), the output parameter values were available only after the SqDataReader was closed.
      • The SqlConnection object did not need to be closed for the parameters to be available, but they were available if it was closed.
    • Using a SqlDataAdapter (SqlDataAdapter adapter = new SqlDataAdapter(cmd)) with the command built in the exact same way as for ExecuteReader(), the output parameter values were null after creating the adapter, but no longer null after calling adapter.Fill.
      • The connection does not need to be closed for the values to be available.

    Clearly this indicates that the result set of ExecuteReader does not actually complete until the reader has been closed, and therefore the output parameter values are not yet available. In the case of an adapter, the fill procedure is done in one shot, and then the dataset is disconnected.

    Hope this helps,

    Jack

    Monday, March 1, 2010 11:02 PM
  • User-319574463 posted

    However,  if I alter the SP and remove the select line, the c# code works and returns the value 5.

    This is a known problem with ADO.NET whereby a dataset has to be read to completion before the output parameters are read.

    Saturday, March 13, 2010 10:24 AM
  • User1263371605 posted

    Thank you i was facing the same issue got resolved by closing the reader.

    Tuesday, April 6, 2010 1:20 PM
  • User441759795 posted

    Glad to know the problem is solved.

    For a comprehensive discussion on how to connect to a SQL Server database from C# database applications as well as Java database applications, click on this link: HOW TO: SQL & C# .

    Here you will find detatiled information on how to connect to SQL Server database, how to pass embedded SQL queries, calling stored procedures, pass parameter etc.


    Shahriar Nour Khondokar

    Monday, May 31, 2010 9:23 AM
  • User-1803393670 posted

    What you need to do is to close the data reader before retrieving its value as explained in 

    http://amilagm.com/2010/11/output-variable-values-not-returned-from-sql-server-sp-in-c-sharp/


    • Marked as answer by Anonymous Thursday, October 7, 2021 12:00 AM
    Tuesday, November 16, 2010 12:11 AM