存储过程为:
CREATE PROCEDURE Get
    @userName varchar
AS
    select * from T_UserInfo
        where  @userName = UserName
GO

------------------------------------
表 T_UserInfo
UserName  UserPWD
  a          a
  asd        asd
-------------------------------------

代码:
using System;
using System.Data;
using System.Data.SqlClient;

class A
{
    public static void Main()
    {
        string userName = "aa";
        string strConn = "server=(local);database=BookManagerSystem;Trusted_Connection=yes;";

        SqlConnection conn = new SqlConnection(strConn);
        SqlCommand comm = new SqlCommand("Get", conn);
        comm.CommandType = CommandType.StoredProcedure;
        try
        {
            conn.Open();

            comm.Parameters.Add("@userName", SqlDbType.NVarChar);
            comm.Parameters["@userName"].Value = userName;

            SqlDataReader reader = comm.ExecuteReader();
            while(reader.Read())
            {
                Console.WriteLine(reader["UserName"]);
                Console.WriteLine(reader["UserID"]);
                Console.WriteLine(reader["UserPWD"]);
                Console.WriteLine(reader["UserPop"]);
            }
        }

        catch(Exception ex)
        {
            Console.WriteLine( ex);
        }
        finally
        {
            conn.Close();
        }
        Console.ReadLine();

    }
}
--------------------------------------------------

运行结果
a
a
---------------------------------------------------

为什么输入的asd,却返回a的内容?哪里有问题?