title: C# ADO.NET IBM DB2 named parameters with same name throws Not enough parameters specified Exception
body: <p>I have a <em>fairly</em> agnostic ADO.NET application that connects to a number of databases and is able to extract the necessary information to run.  I have hit a snag with DB2 and how it handles named parameters, particularly when I reuse a named parameter in the same query.  I know of a couple of ways to get around this by simply adding more parameters, but in theory it should work as it does on other databases that I connect to as the parameter name is the same.</p>
  
  <p>What I'm doing is a bit more complicated and involves subqueries etc, but to demonstrate, take the following query:</p>
  
  <p>select value from test.table where cola=@key1 and colb=@key1;</p>
  
  <p>The named parameter @key1 is used twice.</p>
  
  <p>My code is as follows:</p>
  
  <pre><code>       try
          {
              DbProviderFactory dbfFactory = DbProviderFactories.GetFactory("IBM.Data.DB2.iSeries");
              using (DbConnection dbConnection = dbfFactory.CreateConnection())
              {
                  dbConnection.ConnectionString = "DataSource=xxx.xxx.xxx.xxx;UserID=xxxxxxxx;password=xxxxxxxxx";
  
                  using (DbCommand dbCommand = dbConnection.CreateCommand())
                  {
                      IDbDataParameter iddpParameter1 = dbCommand.CreateParameter();
                      iddpParameter1.ParameterName = "@key1";
                      iddpParameter1.DbType = DbType.String;
                      iddpParameter1.Value = "1";
  
                      dbCommand.Parameters.Add(iddpParameter1);
                      dbCommand.CommandType = CommandType.Text;
                      dbCommand.CommandText = "select value from test.table where cola=@key1 and colb=@key1";
                      dbConnection.Open();
  
                      using (IDataReader idrReader = dbCommand.ExecuteReader())
                      {
                          while (idrReader.Read())
                          {
                                     ...
                          }
                      }
                  }
  
              } // end dbConnection
          } // end try
  
          catch (Exception ex)
          {
              Console.Write(ex.Message);
          }
  </code></pre>
  
  <p>When I run this I get an exception that tells me:</p>
  
  <pre><code>System.InvalidOperationException: Not enough parameters specified.  The command requires 2 parameter(s), but only 1 parameter(s) exist in the parameter collection.
  </code></pre>
  
  <p>I get what it is telling me, but I'm looking for help in figuring out how I can have the provider use the named parameter for both parameters as they are the same.  It seems that it is doing a blind count of named parameters and not realizing that they are the same named parameters.  SQL Server seems to allow me to do this with the same code above.   I'm guessing it's just one of those differences in the providers, but hoping someone has run into this and has a solution for DB2 that doesn't get into specific DB2 code.</p>
  
  <p>Thanks, appreciate the assistance.</p>