設置NULL日期

Question

我的數據庫中有一個日期字段，當用戶單擊某個按鈕將其停用時，客戶被設置爲非活動狀態時，會設置該日期字段。我在嘗試找出如何在用戶試圖響應客戶時清除非活動日期方面遇到困難。

這是解除按鈕的代碼是什麼樣子：

Private Sub btnDeactivate_Click(sender As System.Object, e As EventArgs) Handles btnDeactivate.Click 
     Dim selectedCustomers = GetSelectedCustomers() 
     Dim newInActiveFlag = Not selectedCustomers.Any(Function(c) (c.Inactive_Flag = "Y")) 
     Dim activateWord = "Activate" 
     If newInActiveFlag Then 
      activateWord = "Deactivate" 
     End If 

     Dim result As DialogResult = MessageBox.Show(String.Format("Are you sure you want to {0} this Customer?", activateWord.ToLower()), activateWord + " Customer", _ 
                MessageBoxButtons.YesNo, MessageBoxIcon.Question) 
     If result = Windows.Forms.DialogResult.Yes Then 

      Dim selectedCustomerIds = selectedCustomers.Select(Function(c) (c.Cust_Num)) 

      Dim service = New DataService() 

      service.Customers.SetInactiveFlags(selectedCustomerIds, newInActiveFlag) 
      service.SaveChanges() 
      PerformSearch(_lastSearchTxt, _lastIncludeActive) 
     End If 
    End Sub 

這裏是它設置無效標誌和日期片：

Public Sub SetInactiveFlags(custIds As IEnumerable(Of Integer), inactiveFlag As Boolean) 
     Dim customers As List(Of Customer) 
     customers = _context.Customers.Where(Function(c) (custIds.Contains(c.Cust_Num))).ToList() 

     For Each customer As Customer In customers 
      customer.Inactive_Flag = CreateFromBoolean(inactiveFlag) 
      customer.Inactive_Date = DateTime.Today 
     Next 

    End Sub 

是否有可能有相同的按鈕設置並按照我設置並刪除非活動標誌的方式刪除日期？

感謝

Answer 1

假設你正在讓你的Inactive_Date場null值，你可以簡單地將它設置爲Nothing。如果更改SetInactiveFlags方法有一個可爲空（中DATETIME）參數（？或日期時間ALA C＃快捷鍵），你可以直接通過它跨越：

Public Sub SetInactiveFlags(custIds As IEnumerable(Of Integer), inactiveDate As DateTime?, inactiveFlag As Boolean) 
... 
customer.Inactive_Date = inactiveDate 
... 

那麼您可以使用SetInactiveFlags(selectedCustomerIds, Nothing, newInActiveFlag)或SetInactiveFlags(selectedCustomerIds, DateTime.Now, newInActiveFlag)

實體框架/ Linq2Sql將自動將Nothing轉換爲DBNull.Value。

Answer 2

好吧，我想我找到了解決方案，我把湯姆的意見，並已將此添加到BTN單擊事件：

If activateWord = "Deactivate" Then 
       service.Customers.SetInactiveFlags(selectedCustomerIds, DateTime.Today, newInActiveFlag) 
      ElseIf activateWord = "Activate" Then 
       service.Customers.SetInactiveFlags(selectedCustomerIds, Nothing, newInActiveFlag) 
      End If 

等等全片看起來是這樣的：

Private Sub btnDeactivate_Click(sender As System.Object, e As EventArgs) Handles btnDeactivate.Click 
     Dim selectedCustomers = GetSelectedCustomers() 
     Dim newInActiveFlag = Not selectedCustomers.Any(Function(c) (c.Inactive_Flag = "Y")) 
     Dim activateWord = "Activate" 
     If newInActiveFlag Then 
      activateWord = "Deactivate" 
     End If 

     Dim result As DialogResult = MessageBox.Show(String.Format("Are you sure you want to {0} this Customer?", activateWord.ToLower()), activateWord + " Customer", _ 
                MessageBoxButtons.YesNo, MessageBoxIcon.Question) 
     If result = Windows.Forms.DialogResult.Yes Then 

      Dim selectedCustomerIds = selectedCustomers.Select(Function(c) (c.Cust_Num)) 

      Dim service = New DataService() 
      If activateWord = "Deactivate" Then 
       service.Customers.SetInactiveFlags(selectedCustomerIds, DateTime.Today, newInActiveFlag) 
      ElseIf activateWord = "Activate" Then 
       service.Customers.SetInactiveFlags(selectedCustomerIds, Nothing, newInActiveFlag) 
      End If 
      service.SaveChanges() 
      PerformSearch(_lastSearchTxt, _lastIncludeActive) 
     End If 
    End Sub 

我也改了SetInactiveFlags看起來像這樣：

Public Sub SetInactiveFlags(custIds As IEnumerable(Of Integer), Inactive_Date As DateTime?, inactiveFlag As Boolean) 
     Dim customers As List(Of Customer) 
     customers = _context.Customers.Where(Function(c) (custIds.Contains(c.Cust_Num))).ToList() 

     For Each customer As Customer In customers 
      customer.Inactive_Flag = CreateFromBoolean(inactiveFlag) 
      customer.Inactive_Date = Inactive_Date 
     Next 

    End Sub 

我花了一分鐘來了解邏輯，但感謝羚牛克時間來幫助我，我真的很感激它。