关于存储过程输出参数的问题，各位高手请进!

[stoway]

我在vb.net中调用存储过程时，若有输出参数或返回值，总是出现错误，代码如下：
'con已在模块中定义完
Dim com As New SqlClient.SqlCommand()
com.Connection = con
com.CommandType = CommandType.StoredProcedure
com.Parameters.Add(New SqlClient.SqlParameter("@Return_Val", System.Data.SqlDbType.Int, 1, ParameterDirection.ReturnValue))
com.Parameters.Add(New SqlClient.SqlParameter("@McDate", System.Data.SqlDbType.Char, 10, ParameterDirection.Input))
com.Parameters.Add(New SqlClient.SqlParameter("@McStartTime", System.Data.SqlDbType.Char, 5, ParameterDirection.Input))
com.Parameters.Add(New SqlClient.SqlParameter("@McEndTime", System.Data.SqlDbType.Char, 5, ParameterDirection.Input))
com.Parameters.Add(New SqlClient.SqlParameter("@McRestTime", System.Data.SqlDbType.Decimal))
com.Parameters(3).Direction = ParameterDirection.Input
com.Parameters(1).Value = DateData
com.Parameters(2).Value = StartTime
com.Parameters(3).Value = EndTime
com.Parameters(4).Value = RestTime
Select Case OperStyle
Case "insert"
com.CommandText = "Msp_AddNew"
Case "update"
com.CommandText = "Msp_Update"
'com.Parameters.Add(new SqlClient.SqlParameter(
Case "delete"
com.CommandText = "Msp_Delete"
End Select
com.ExecuteNonQuery()
一到上一句就提示我系统错误，请各位指点!

[saucer]

catch the error, and show the detailed error messages

Try
'your code goes here
Catch ex As SqlException
Response.Write (ex.Message)
Finally
con.Close
End Try

[Flattron]

看微软的101个例子，非常详细