C#执行含事务的存储过程

存储过程如下：

USE[TestDB]
GO
IF EXISTS (SELECT * FROM dbo.sysobjects WHERE id = OBJECT_ID(N'[dbo].[USP_ProcedureWithTransaction_Demo]') and OBJECTPROPERTY(id, N'IsProcedure') = 1) 
DROP PROCEDURE [dbo].[USP_ProcedureWithTransaction_Demo] 
GO
-- =============================================
-- Author:        <>
-- Create date: <>
-- Description:    <存储过程中使用事务>
-- =============================================
CREATE PROCEDURE [dbo].[USP_ProcedureWithTransaction_Demo]
AS
BEGIN
    BEGIN TRY
        BEGIN TRANSACTION
            UPDATE dbo.test SET num = 1 WHERE TypeID = 1;
            UPDATE dbo.test SET num = 4 WHERE TypeID = 2; --此语句将出错，Phone为Int类型
            UPDATE dbo.test SET num = 'c' WHERE TypeID = 3;
        COMMIT TRANSACTION
    END TRY
    BEGIN CATCH
        ROLLBACK TRANSACTION
        RETURN -1;
    END CATCH    
    RETURN 1;
END

 c#执行此存储过程

/// <summary>
        /// 执行存储过程，无参数，有返回值。存储过程执行成功时返回1，否则返回0。
        /// </summary>
        /// <param name="spName">存储过程名称</param>
        /// <returns>0：出错；1：成功</returns>
        public int SpWithReturnValueExecuteNonQuery(string spName)
        {
            int result = 0;
            SqlConnection cnn = GetConnection();
            SqlTransaction trans = null;
            SqlCommand cmd = new SqlCommand(spName, cnn);

            cmd.Parameters.Add("@ReturnValue", SqlDbType.Int).Direction = ParameterDirection.ReturnValue;

            cmd.CommandTimeout = _commandTimeout;
            cmd.CommandType = CommandType.StoredProcedure;

            try
            {
                cmd.ExecuteNonQuery();
                result = (int)cmd.Parameters["@ReturnValue"].Value;
            }
            catch (SqlException)
            {
                return result;
            }
            finally
            {
                cnn.Close();
            }
            return result;
        }