你调用的对象是空的。我能从这些错误中得到帮助吗？ [英] Object reference not set to an instance of an object. can I get Help form these error

问题描述

DropDownList status =（DropDownList）DemoGridView.FooterRow.FindControl（FooterStatus）;

..........



...........

catch（execption e）//获取错误：对象引用未设置为对象的实例。

{

}

解决方案

在您的代码中，DemoGridView.FooterRow可能为null，这就是为什么你有这个例外或在页脚没有FooterStatus名称的对象。

  foreach （GridViewRow  DemoGridView.Rows中的行 {
  if （row.RowType == DataControlRowType.DataRow） {
 DropDownList status = row.FindControl（  FooterStatus） as  DropDownList; 
} 
} 

 <   asp：TemplateField     HeaderText   = 状态 >  
 
 <   ItemTemplate  >  
 <   asp：Label     ID   =  lblStatus < span class =code-attribute>   runat   =  server  
   
                            < span class =code-attribute>                                  文字  ='  <％ #Bind（ 状态）< span class =code-pagedirective>％> ' >  <   / asp：标签 >  
 <   / ItemTemplate  >  
 <   EditItemTemplate  >  
 <   asp：DropDownList     ID   =  EditStatus    runat   = 服务器 >  
 <％  - < asp：ListItem>已婚< /   asp：ListItem  >  
 <  < span class =code-leadattribute> asp：ListItem  > 未婚<  < span class =code-leadattribute> / asp：ListItem  >  
 <   asp：ListItem  > 无<   / asp：ListItem  >   - ％> 
 <   / asp：DropDownList  >  
 
 <   / EditItemTemplate  >  
 <   FooterTemplate  >  
 <   asp：DropDownList     ID   =  FooterStatus    runat   =  服务器 >  
 <％  - < asp：ListItem>已婚< /   asp：ListItem  >  
 <   asp：ListItem  > 未婚<   / asp：ListItem  >  
 <   asp：ListItem  > 无<   / asp：ListItem  >   - ％> 
 <   / asp：DropDownList  >  
 <   / FooterTemplate   >  
 <   / asp：TemplateField  >  

DropDownList status = (DropDownList)DemoGridView.FooterRow.FindControl("FooterStatus");
..........

...........
catch(execption e)// Getting an error: Object reference not set to an instance of an object.
{
}

解决方案

In your code DemoGridView.FooterRow is probably null that's why you've got that exception or in the footer there is no object with FooterStatus name.

foreach(GridViewRow row in DemoGridView.Rows) {
    if(row.RowType == DataControlRowType.DataRow) {
        DropDownList status = row.FindControl("FooterStatus") as DropDownList;
    }
}

<asp:TemplateField HeaderText="Status">

                      <ItemTemplate>
                          <asp:Label ID="lblStatus" runat="server"

                              Text='<%# Bind("Status") %>'></asp:Label>
                      </ItemTemplate>
                      <EditItemTemplate>
                          <asp:DropDownList ID="EditStatus" runat="server">
                              <%--<asp:ListItem>Married</asp:ListItem>
                  <asp:ListItem>Unmarried</asp:ListItem>
                  <asp:ListItem>None</asp:ListItem>--%>
                          </asp:DropDownList>

                      </EditItemTemplate>
                      <FooterTemplate>
                          <asp:DropDownList ID="FooterStatus" runat="server">
                              <%-- <asp:ListItem>Married</asp:ListItem>
                  <asp:ListItem>Unmarried</asp:ListItem>
                  <asp:ListItem>None</asp:ListItem>--%>
                          </asp:DropDownList>
                      </FooterTemplate>
                  </asp:TemplateField>

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