即使執行成功，C＃對象也不能從DBNull錯誤轉換

我試圖更新數據庫中的值（同時返回狀態信息）並獲取以下InvalidCastError - 對象無法從DBNull轉換爲其他類型。但是，信息在數據庫中更新。它似乎不想回到'真實'或成功的等值。如下圖所示代碼：即使執行成功，C＃對象也不能從DBNull錯誤轉換

C＃：

public bool Update(Customer pCustomer) 
    { 
     using (SqlConnection sqlConnect = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString)) 
     { 
      using (SqlCommand sqlComm = new SqlCommand("Update_Customer", sqlConnect)) 
      { 
       sqlComm.CommandType = CommandType.StoredProcedure; 
       //Other items to update (Not causing issues) 

       sqlComm.Parameters.Add("@Message", SqlDbType.Bit).Direction = ParameterDirection.Output; 
       sqlComm.Connection = sqlConnect; 

       try 
       { 
        sqlComm.Connection.Open(); 
        sqlComm.ExecuteNonQuery(); 
        return Convert.ToBoolean(sqlComm.Parameters["@Message"].Value); 
       } 

       catch(Exception) 
       { 
        throw; 
       } 

       finally 
       { 
        sqlComm.Connection.Close(); 
       } 
      } 
     } 
    }

SQL：

 //Unrelevent code removed 
    AS 
BEGIN 
    BEGIN TRY 
     BEGIN TRAN 
      BEGIN 
       UPDATE Customer 
       SET 
        Password = @Password, 
        RecordTimeStamp = @NewRecordTimeStamp 
       WHERE CustomerID = @CustomerID AND RecordTimeStamp = @OldRecordTimeStamp 
      END 
      IF @@ROWCOUNT <> 1 
       BEGIN 
        Set @Message = 1 
       END 
     IF @@ERROR <> 0 
      ROLLBACK TRAN 
     ELSE 
      COMMIT TRAN 
    END TRY 
    BEGIN CATCH 
     DECLARE @Err nvarchar(500) 
     SET @Err = ERROR_MESSAGE() 
     RAISERROR(@Err, 16, 1) 
    END CATCH 
END 
GO

來源

2013-02-27 ZeeeeeV

你檢查，看看是否有任何您發送或返回是'null'？ – Brian 2013-02-27 22:32:10

一切都有一個值，它在數據庫中正確更新。只是似乎沒有註冊成功更新。 – ZeeeeeV 2013-02-27 22:32:54

好吧，數據庫中的所有內容都更新了，但是'@ Message'裏面有「True」還是「False」？ – 2013-02-27 22:34:00

以一個猜測，我覺得sqlComm.Parameters["@Message"].Value將返回System.DBNull.Value。

是否有可能@@ROWCOUNT等於1那麼因此@Message沒有被設置？

來源

2013-02-27 22:34:28

+1 - 看起來你打敗了我的答案。 – 2013-02-27 23:08:40

除非我的T-SQL是可怕的，這應該工作。

BEGIN 
    SET @Message = 0; 

    BEGIN TRANSACTION 

    BEGIN TRY 
     UPDATE Customer 
     SET Password  = @Password, 
      RecordTimeStamp = @NewRecordTimeStamp 
     WHERE CustomerID = @CustomerID 
     AND RecordTimeStamp = @OldRecordTimeStamp 

     IF @@ROWCOUNT <> 1 
      Set @Message = 1; 

     COMMIT TRANSACTION 
    END TRY 
    BEGIN CATCH 

     DECLARE @Err nvarchar(500) 
     SELECT @Err = ERROR_MESSAGE() 
     RAISERROR(@Err, 16, 1) 

     ROLLBACK TRANSACTION 
    END CATCH 
END

來源

2013-02-27 23:19:48 Romoku

AS 
BEGIN 
Set @Message = 0 
    BEGIN TRY 
     BEGIN TRAN 
      BEGIN 
       UPDATE Customer 
       SET 
        Password = @Password, 
        RecordTimeStamp = @NewRecordTimeStamp 
       WHERE CustomerID = @CustomerID AND RecordTimeStamp = @OldRecordTimeStamp 
      END 
      IF @@ROWCOUNT = 1 
        Set @Message = 1 
      END 
      IF @@ERROR <> 0 
      ROLLBACK TRAN 
      ELSE 
      COMMIT TRAN 
    END TRY 
    BEGIN CATCH 
     DECLARE @Err nvarchar(500) 
     SET @Err = ERROR_MESSAGE() 
     RAISERROR(@Err, 16, 1) 
    END CATCH 
END 
GO

來源

2013-02-27 23:33:05

即使執行成功，C＃對象也不能從DBNull錯誤轉換

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