对象引用未设置为对象的实例 [英] object refrence not set to an instance of and object

问题描述

你好先生，

i有数据控制权。

hello sir,
i have datalist control.

<asp:DataList ID="DataList1" runat="server"/>
            <HeaderTemplate>
                CATEGORY</HeaderTemplate>
            <itemstyle backcolor="White" forecolor="Black" borderwidth="2px" />
            <itemtemplate>
               <asp:Image ID="Image1" runat="server" Height="150px" Width="100px" ImageUrl='<%# "hangler_reward.ashx?category=" + Eval("category") %>' style="padding-left:40px;"/><br />

                CATEGORY NAME
 
                <asp:LinkButton ID="lnkcat" runat="server" Text='<%# Bind("CATEGORY") %>' 
                    onclick="lnkcat_Click">
 
                <br />

            </itemtemplate>

这是linkbutton click事件。

this is linkbutton click event.

protected void lnkcat_Click(object sender, EventArgs e)
    {
      //  string text = ((LinkButton)DataList1.FindControl("lnkcat")).Text;
        string text = ((LinkButton)DataList1.FindControl("lnkcat")).Text;
    }

i想找到链接按钮text但是有错误

对象refrence未设置为对象的实例

i want to find link button "text" but there is error
"object refrence not set to an instance of and object"

推荐答案

因为DataList1.FindControl（lnkcat）返回null：DataList1找不到名为lnkcat的控件 -

甚至更糟：DataList1可能为空。

为什么不使用click事件的sender参数？

Something喜欢

Because DataList1.FindControl("lnkcat") returned null: DataList1 did not find a control with the name "lnkcat" -
or even worse: DataList1 could be null.
Why don't you use the sender parameter of the click event?
Something like

protected void lnkcat_Click(object sender, EventArgs e)
{
    LinkButton btn = sender as LinkButton;
    if (btn == null)
    {
         // write it to the log or deal somehow with it, then
         return;
    }
    string text = btn.Text;
}

string text ="";
LinkButton lbtn= (LinkButton )this.DataList1.FindControl("lnkcat");
text = lbtn.Text.toString();

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