从ADO.NET中的存储过程获取返回值

Question

我知道还有另一个问题,几乎相同的标题,但它没有回答我的问题.我有一个存储过程,它在插入后返回唯一标识符(@@ identity).我在服务器资源管理器中尝试了它,它按预期工作(@RETURN_VALUE = [identifier]).在我的代码中,我添加了一个名为"@RETURN_VALUE"的参数,其中ReturnValue方向优先于任何其他参数,但是当我使用ExecuteNonQuery()运行我的查询时该参数保持为空.我不知道我做错了什么.我的SPROC:

    ALTER PROCEDURE dbo.SetAuction
 (
  @auctionID int,
  @itemID int,
  @auctionType tinyint,
  @reservationPrice int,
  @maxPrice int,
  @auctionEnd datetime,
  @auctionStart datetime,
  @auctionTTL tinyint,
  @itemName nchar(50),
  @itemDescription nvarchar(MAX),
  @categoryID tinyint,
  @categoryName nchar(50)
 ) AS
 IF @auctionID <> 0
  BEGIN
   BEGIN TRAN T1

   UPDATE Auction
   SET  AuctionType   = @auctionType,
     ReservationPrice = @reservationPrice,
     MaxPrice    = @maxPrice,
     AuctionEnd    = @auctionEnd,
     AuctionStart   = @auctionStart,
     AuctionTTL    = @auctionTTL
   WHERE AuctionID    = @auctionID;

   UPDATE Item
   SET
    ItemName  = @itemName,
    ItemDescription = @itemDescription
   WHERE
    ItemID = (SELECT ItemID FROM Auction WHERE AuctionID = @auctionID);

   COMMIT TRAN T1

   RETURN @auctionID
  END
 ELSE
  BEGIN
   BEGIN TRAN T1
    INSERT INTO Item(ItemName, ItemDescription, CategoryID)
    VALUES(@itemName, @itemDescription, @categoryID);

    INSERT INTO Auction(ItemID, AuctionType, ReservationPrice, MaxPrice, AuctionEnd, AuctionStart, AuctionTTL)
    VALUES(@@IDENTITY,@auctionType,@reservationPrice,@maxPrice,@auctionEnd,@auctionStart,@auctionTTL);
   COMMIT TRAN T1
   RETURN @@IDENTITY
  END

我的代码是:

                cmd.CommandText = cmdText;
                SqlParameter retval = new SqlParameter("@RETURN_VALUE", System.Data.SqlDbType.Int);
                retval.Direction = System.Data.ParameterDirection.ReturnValue;
                cmd.Parameters.Add(retval);
                cmd.Parameters.AddRange(parameters);
                cmd.Connection = connection;

                connection.Open();
                cmd.ExecuteNonQuery();

                return (int)cmd.Parameters["@RETURN_VALUE"].Value;

Answer 1

刚尝试我的盒子,这对我有用:

在SQL Server中:

DROP PROCEDURE TestProc;
GO
CREATE PROCEDURE TestProc
AS
   RETURN 123;
GO

在C#中

        string cnStr = "Server=.;Database=Sandbox;Integrated Security=sspi;";
        using (SqlConnection cn = new SqlConnection(cnStr)) {
            cn.Open();
            using (SqlCommand cmd = new SqlCommand("TestProc", cn)) {
                cmd.CommandType = CommandType.StoredProcedure;
                SqlParameter returnValue = new SqlParameter();
                returnValue.Direction = ParameterDirection.ReturnValue;
                cmd.Parameters.Add(returnValue);

                cmd.ExecuteNonQuery();
                Assert.AreEqual(123, (int)returnValue.Value);
            }
        }

Answer 2

我解决了这个问题：您必须设置SqlCommand.CommandType为CommandType.StoredProcedure以获得返回值和/或输出参数。我还没有找到任何相关文档，但是现在一切正常。