vb.net 运算符 '=' 未为类型 'DBNull' 和类型 'Boolean' 定义。??/
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Operator '=' is not defined for type 'DBNull' and type 'Boolean'.??/
提问by Ashley Smith
I am going to count the checked and unchecked check box in my attendance but that come out in my code."Operator '=' is not defined for type 'DBNull' and type 'Boolean'.??"... pls help..your help is greatly appreciated. thanks
我将计算出勤中选中和未选中的复选框，但这会出现在我的代码中。“运算符 '=' 未为类型 'DBNull' 和类型 'Boolean' 定义。??”...请帮忙。非常感谢您的帮助。谢谢
my code:
我的代码：
Next
下一个
Dim Present As Integer = 0
Dim Absent As Integer = 0
For a = 0 To Table2___lieDataGridView.RowCount - 1
For b = 0 To Table2___lieDataGridView.ColumnCount - 8
If Table2___lieDataGridView.Rows(a).Cells(b + 5).Value = True Then
Present += 1
Else
Absent += 1
End If
Next
Table2___lieDataGridView.Rows(a).Cells(10).Value = Present
Table2___lieDataGridView.Rows(a).Cells(11).Value = Absent
Present = 0
Absent = 0
Next
回答by Alex Wiese
回答by user3782235
Before you compare the Value to True, you should check if the Value is NOT actually DBNull type. It is because you happen to have null values in your database, and there is no comparative operator against boolean for that situation.
在将 Value 与 True 进行比较之前，您应该检查 Value 是否实际上不是 DBNull 类型。这是因为您的数据库中碰巧有空值，并且在这种情况下没有针对布尔值的比较运算符。
For example, look this question: Handling DBNull data in VB.Net
例如，看这个问题：在 VB.Net 中处理 DBNull 数据
