ADO.NET - Trouble Getting Output Parameter - sql-server

Question

My DBA created the following Stored Proc which he insists works fine when called in SQL Server:
CREATE procedure [dbo].[GetParentID]
#SSHIP_AppID as varchar(50),
#ParentID as varchar(150) OUTPUT
AS
BEGIN
SET NOCOUNT ON;
SELECT #ParentID = a.iBuild_GUID
FROM dbo.XRef_iBuild_SSHIP as a
WHERE a.SSHIP_appId = #SSHIP_AppID
AND a.SSHIP_appId <> ''
END
I have created the following ADO.NET Wrapper but I am having trouble getting the output parameter. I keep getting back "OUTPUT" as its value:
private string GetParentId(string appId)
{
var connection = new SqlConnection();
string parentId = String.Empty;
try
{
connection.ConnectionString = "...)
var command = new SqlCommand("GetParentId", connection);
command.CommandType = CommandType.StoredProcedure;
command.Parameters.Add(new SqlParameter("#SSHIP_AppID", appId));
command.Parameters.Add(new SqlParameter("#ParentID", ParameterDirection.Output));
connection.Open();
command.ExecuteNonQuery();
parentId = (command.Parameters["#ParentId"].Value).ToString();
}
catch (Exception ex)
{
LogError(appId, ex.ToString(), "Interface12 - Cannot get ParentId", null, 0);
}
finally
{
connection.Close();
}
return parentId;
}
}
What am I doing wrong?

Answer 1

In new SqlParameter("#ParentID", ParameterDirection.Output) the 2nd argument is treated as the object value argument and apparently converted to a string.
(This implicit conversion is, in my opinion, a design flaw in ADO.NET. It should throw an exception for any unknown input type.).
Choose a better overload.