如何：用 Windows 窗体 DataGrid 控件验证输入

更新：2007 年 11 月

说明：
DataGridView 控件替换了 DataGrid 控件并添加了功能；但是也可选择保留 DataGrid 控件以备向后兼容和将来使用。有关更多信息，请参见 Windows 窗体 DataGridView 控件和 DataGrid 控件之间的区别。

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。

另一种输入验证类型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 就属于不可接受的数据。此外，不合适的字符串也是不可接受的数据。这是在数据集中通过编写 ColumnChanging 或 RowChanging 事件的事件处理程序来完成的。下面的示例使用 ColumnChanging 事件，因为“Product”列不接受不允许的值。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”列的值。

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。

   Private Sub Customers_ColumnChanging(ByVal sender As Object, _
   ByVal e As System.Data.DataColumnChangeEventArgs)
      ' Only check for errors in the Product column
      If (e.Column.ColumnName.Equals("Product")) Then
         ' Do not allow "Automobile" as a product.
         If CType(e.ProposedValue, String) = "Automobile" Then
            Dim badValue As Object = e.ProposedValue
            e.ProposedValue = "Bad Data"
            e.Row.RowError = "The Product column contians an error"
            e.Row.SetColumnError(e.Column, "Product cannot be " & _
            CType(badValue, String))
         End If
      End If
   End Sub
   

   //Handle column changing events on the Customers table
   private void Customers_ColumnChanging(object sender, System.Data.DataColumnChangeEventArgs e) {
   
      //Only check for errors in the Product column
      if (e.Column.ColumnName.Equals("Product")) {
   
         //Do not allow "Automobile" as a product
         if (e.ProposedValue.Equals("Automobile")) {
            object badValue = e.ProposedValue;
            e.ProposedValue = "Bad Data";
            e.Row.RowError = "The Product column contains an error";
            e.Row.SetColumnError(e.Column, "Product cannot be " + badValue);
         }
      }
   }
   

   //Handle column changing events on the Customers table
   private void Customers_ColumnChanging(System.Object sender, System.Data.DataColumnChangeEventArgs e) 
   {
      //Only check for errors in the Product column
      if ( e.get_Column().get_ColumnName().Equals("Product") ) 
      {
         //Do not allow "Automobile" as a product
         if ( e.get_ProposedValue().Equals("Automobile") ) 
         {
            System.Object badValue = e.get_ProposedValue();
            e.set_ProposedValue("Bad Data");
            e.get_Row().set_RowError("The Product column contains an error");
            e.get_Row().SetColumnError(e.get_Column(), "Product cannot be " + badValue);
         }
      }
   }
   

2. 将事件处理程序连接到事件。

   将下面的代码置于窗体的 Load 事件或其构造函数内。

   ' 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
   

   // 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);
   

   // 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.get_Tables().get_Item("Customers").add_ColumnChanging(
      new DataColumnChangeEventHandler(this.Customers_ColumnChanging));
   

请参见

参考

DataGrid

ColumnChanging

SetColumnError

其他资源

DataGrid 控件（Windows 窗体）