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Error on Parameterized Queries using Enterprise Library 4.0

Posted on 2008-10-14
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Last Modified: 2008-10-22
I'm creating a simple Data Access Layer for an app using the Enterprise Library 4.0. I can execute simple sql queries and they return data. However, when I try to create a "Parameterized Query"  the following exceptio occurs.

System.Data.SqlClient.SqlException was caught
  Message="Parameterized Query '(@symbol_id int)Select * from Symbol where [symbol_id] = @symbol' expects parameter @symbol_id, which was not supplied."
  Source=".Net SqlClient Data Provider"

The parameter never gets set and I can't see why!!
 

private static readonly string SQL_SELECT = @"Select * from Symbol where [symbol_id] = @symbol_id";
        
        public IDataReader Select(System.Nullable<int> id)
        {
            try
            {
                Database db = DatabaseFactory.CreateDatabase("myConnection");
                DbCommand cmd = db.GetSqlStringCommand(SQL_SELECT);
                cmd.Parameters.Add(new SqlParameter("@symbol_id", SqlDbType.Int));
                cmd.Parameters["@symbol_id"].Value = id;
                return db.ExecuteReader(cmd);
            }
            catch
            {
                throw;
            }
        }

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Question by:johnaryan
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3 Comments
 
LVL 5

Author Comment

by:johnaryan
ID: 22716667
Just realised it didn't like when I passed in a null value.
I fixed it like this(changed line 4)

Does anyone have a better solution?

Database db = DatabaseFactory.CreateDatabase("myConnection");
DbCommand cmd = db.GetSqlStringCommand(SQL_SELECT);
cmd.Parameters.Add(new SqlParameter("@symbol_id", SqlDbType.Int));
cmd.Parameters["@symbol_id"].Value = id==null?DBNull.Value:(object)id;
return db.ExecuteReader(cmd);

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Accepted Solution

by:
Anurag Thakur earned 1000 total points
ID: 22718316
dont do a boxing operation as in (object)id;
cmd.Parameters["@symbol_id"].Value = id == null ? DBNull.Value : id;
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LVL 5

Author Comment

by:johnaryan
ID: 22718884
I don't have the code in front of me now, but wouldn't I get an Invalid conversion?
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