用 Windows 窗体 DataGrid 控件验证输入

Windows 窗体 DataGrid 控件有两种可用的输入验证类型。如果用户试图输入一个值，而该值具有单元格不可接受的数据类型（例如，向需要整数的单元格中输入一个字符串），则新的无效值将替换为旧值。这种输入验证是自动完成的，不能进行自定义。

另一种的输入验证可用于拒绝任何不可接受的数据，例如，在必须大于或等于 1 的字段中输入 0，或者一个不合适的字符串。这是在数据集中通过编写 DataTable.ColumnChanging 或 DataTable.RowChanging 事件的事件处理程序来完成的。以下示例使用 ColumnChanging 事件，因为“Product”列特别不允许不可接受的值。您可以使用 RowChanging 事件来检查“End Date”列的值是否晚于同一行中“Start Date”的值。

验证用户输入

1.               编写代码以处理相应表的 ColumnChanging 事件。当检测到不适当的输入时，调用 DataRow 对象的 SetColumnError 方法。

2.                    ' Visual Basic

3.                    Private Sub Customers_ColumnChanging(ByVal sender As Object, _

4.                    ByVal e As System.Data.DataColumnChangeEventArgs)

5.                       ' Only check for errors in the Product column

6.                       If (e.Column.ColumnName.Equals("Product")) Then

7.                          ' Do not allow "Automobile" as a product.

8.                          If CType(e.ProposedValue, String) = "Automobile" Then

9.                             Dim badValue As Object = e.ProposedValue

10.                         e.ProposedValue = "Bad Data"

11.                         e.Row.RowError = "The Product column contians an error"

12.                         e.Row.SetColumnError(e.Column, "Product cannot be " & _

13.                         CType(badValue, String))

14.                      End If

15.                   End If

16.                End Sub

17.               

18.                // C#

19.                //Handle column changing events on the Customers table

20.                private void Customers_ColumnChanging(object sender, System.Data.DataColumnChangeEventArgs e) {

21.               

22.                   //Only check for errors in the Product column

23.                   if (e.Column.ColumnName.Equals("Product")) {

24.               

25.                      //Do not allow "Automobile" as a product

26.                      if (e.ProposedValue.Equals("Automobile")) {

27.                         object badValue = e.ProposedValue;

28.                         e.ProposedValue = "Bad Data";

29.                         e.Row.RowError = "The Product column contains an error";

30.                         e.Row.SetColumnError(e.Column, "Product cannot be " + badValue);

31.                      }

32.                   }

}

33.           将事件处理程序连接到事件。

将以下代码置于窗体的 Load 事件或其构造函数内。

' Visual Basic

' Assumes the grid is bound to a dataset called customersDataSet1

' with a table called Customers.

' Put this code in the form's Load event or its constructor.

AddHandler customersDataSet1.Tables("Customers").ColumnChanging, AddressOf Customers_ColumnChanging

// C#

// Assumes the grid is bound to a dataset called customersDataSet1

// with a table called Customers.

// Put this code in the form's Load event or its constructor.

customersDataSet1.Tables["Customers"].ColumnChanging += new DataColumnChangeEventHandler(this.Customers_ColumnChanging);