SqlServer建立存储过程,方便.NET插入自增字段

create table tablesNo
(
    tableName varchar(30) not null,    --表名
    num int not null --行数
)

USE [test]        --数据库名
GO
/****** Object:  StoredProcedure [dbo].[usp_Id]    Script Date: 2017/2/1 星期三 下午 6:48:47 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
create  proc [dbo].[usp_Id]        --新建一个存储过程名为usp_Id
 @tableName nvarchar(50),
 @id int output
as
declare @erro int
set @erro=0
begin transaction
　　select @id=num+1 from tablesNo where tableName=@tableName
　　set @erro=@erro+@@ERROR
　　update tablesNo set num=num+1 where tableName=@tableName
　　set @erro=@erro+@@ERROR
　　if(@erro=0)
　　　　begin
　　　　commit transaction
　　　　end
   else
　　　　begin
　　　　rollback transaction
　　　　end

public class CommonService              
    {
        public static int GetId(string tableName)           //存储过程ID
        {
            int id = 0;
            string sql = "usp_Id";
            SqlParameter par1 = new SqlParameter("@tableName", tableName);
            par1.Direction = ParameterDirection.Input;
            SqlParameter par2 = new SqlParameter("@id", SqlDbType.Int);
            par2.Direction = ParameterDirection.Output;
            SqlConnection con = null;
            SqlCommand cmd = null;
            try
            {
                con = SqlHelper.Open();
                cmd = new SqlCommand();
                cmd.Connection = con;
                cmd.CommandText = sql;
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.Parameters.Add(par1);
                cmd.Parameters.Add(par2);
                cmd.ExecuteNonQuery();
                id = Convert.ToInt32(cmd.Parameters["@id"].Value);

            }
            catch (SqlException ex)
            {

            }
            finally
            {
                con.Close();
            }

            return id;

        }
    }

Id = CommonService.GetId("ClickAccessAmount");