动态地在gridview中添加控件

Question

我需要动态地将控件添加到GridView，所以我添加了一个PlaceHolder，但它给了我一个错误。

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e) 
{ 
    PlaceHolder plachldr = e.Row.FindControl("PlaceHolder2") as PlaceHolder; 
    Button btn = new Button() { ID = "btnShhow", Text = "Show" }; 
    plachldr.Controls.Add(btn); 

    PlaceHolder placeholder = e.Row.FindControl("PlaceHolder1") as PlaceHolder; 
    TextBox txt1 = new TextBox(); 
    placeholder.Controls.Add(txt1); 
} 

同时加入了控制占位符，则是给我下面的错误：

Object reference not set to an instance of an object.

这里的标记为我的GridView：

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" OnSelectedIndexChanging="GridView1_SelectedIndexChanging" onrowdatabound="GridView1_RowDataBound">  
    <Columns> 
     <asp:BoundField DataField="Name" HeaderText="Name" /> 
     <asp:BoundField DataField="Salary" HeaderText="Salary" />  
     <asp:TemplateField> 
      <ItemTemplate> 
       <asp:PlaceHolder ID="PlaceHolder1" runat="server"></asp:PlaceHolder> 
      </ItemTemplate> 
     </asp:TemplateField>  
     <asp:TemplateField> 
      <ItemTemplate> 
       <asp:PlaceHolder ID="PlaceHolder2" runat="server"></asp:PlaceHolder>  
      </ItemTemplate> 
     </asp:TemplateField>  
    </Columns> 
</asp:GridView> 

Answer 1

您需要检查plachldr或占位符为空或者不是，并且还检查RowType

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e) 
{ 

    if(if (e.Row.RowType == DataControlRowType.DataRow) 
    { 
    PlaceHolder plachldr = e.Row.FindControl("PlaceHolder2") as PlaceHolder; 
    if(plachldr!=null) 
    { 
    Button btn = new Button() { ID = "btnShhow", Text = "Show" }; 
    plachldr.Controls.Add(btn); 
    } 

    PlaceHolder placeholder = e.Row.FindControl("PlaceHolder1") as PlaceHolder; 
    if(placeholder!=null) 
    { 
    TextBox txt1 = new TextBox(); 
    placeholder.Controls.Add(txt1); 
    } 
    } 

}