FindControl 返回 Null

Question

我正在尝试根据相关文本框来控制按钮状态。除前缀外，名称相同。文本框和按钮位于页面上的 table 中。

<asp:Table ID="Table1" runat="server" CssClass="table">
            <asp:TableRow>
                <asp:TableCell Width="15%">
                    <asp:Label ID="lblRequestHeader" runat="server" Text="Requested" CssClass="bold text-center"
                        Width="90%"></asp:Label>
                </asp:TableCell>
                <asp:TableCell Width="15%">
                    <asp:Label ID="lblApprovalHeader" runat="server" Text="Approval" CssClass="bold text-center"
                        Width="90%"></asp:Label>
                </asp:TableCell>
                <asp:TableCell Width="15%">
                    <asp:Label ID="lblApprovalTimeHeader" runat="server" Text="Date/Time of Approval"
                        CssClass="bold text-center" Width="90%"></asp:Label>
                </asp:TableCell>
                <asp:TableCell Width="15%">
                    <asp:Label ID="lblReadyHeader" runat="server" Text="Ready To Pick Up" CssClass="bold text-center"
                        Width="90%"></asp:Label>
                </asp:TableCell>
                <asp:TableCell Width="15%">
                    <asp:Label ID="lblCollectedHeader" runat="server" Text="Collected By TestHouse" CssClass="bold text-center"
                        Width="90%"></asp:Label>
                </asp:TableCell>
                <asp:TableCell Width="15%">
                    <asp:Label ID="lblDeliveredHeader" runat="server" Text="Delivered From TestHouse"
                        CssClass="bold text-center" Width="90%"></asp:Label>
                </asp:TableCell>
            </asp:TableRow>
            <asp:TableRow>
                <asp:TableCell Width="15%">
                    <asp:TextBox ID="txtRequestTime" runat="server" Width="90%"> </asp:TextBox>
                </asp:TableCell>
                <asp:TableCell Width="15%">
                    <asp:TextBox ID="txtApproval" runat="server" Width="90%"></asp:TextBox>
                </asp:TableCell>
                <asp:TableCell Width="15%">
                    <asp:TextBox ID="txtApprovalTime" runat="server" Width="90%"></asp:TextBox>
                </asp:TableCell>
                <asp:TableCell Width="15%">
                    <asp:TextBox ID="txtReadyTime" runat="server" Width="90%"></asp:TextBox>
                </asp:TableCell>
                <asp:TableCell Width="15%">
                    <asp:TextBox ID="txtCollectedTime" runat="server" Width="90%"></asp:TextBox>
                </asp:TableCell>
                <asp:TableCell Width="15%">
                    <asp:TextBox ID="txtDeliveredTime" runat="server" Width="90%"></asp:TextBox>
                </asp:TableCell>
            </asp:TableRow>
            <asp:TableRow>
                <asp:TableCell Width="15%">
                </asp:TableCell>
                <asp:TableCell Width="15%">
                </asp:TableCell>
                <asp:TableCell Width="15%">
                </asp:TableCell>
                <asp:TableCell Width="15%">
                    <asp:Button ID="btnReadyTime" runat="server" Text="Ready To Collect" Width="90%" />
                </asp:TableCell>
                <asp:TableCell Width="15%">
                    <asp:Button ID="btnCollectedTime" runat="server" Text="Collected" Width="90%" />
                </asp:TableCell>
                <asp:TableCell Width="15%">
                    <asp:Button ID="btnDeliveredTime" runat="server" Text="Delivered" Width="90%" />
                </asp:TableCell>
            </asp:TableRow>
        </asp:Table>

文本框由数据检索填充，然后按钮的状态由调用的方法设置如下：

txtReadyTime.Text = slabdetails.ReadyTimestamp.ToString();
textboxenabled(txtReadyTime);

此方法将文本框名称修改为按钮名称，然后尝试找到按钮 enable/disable 它。

 public void textboxenabled(TextBox box)
    {
       string btnName = box.ID.Replace("txt", "btn");
        try
        {
            Button btn = FindControl(btnName) as Button;
            if (box.Text == "")
                btn.Enabled = true;
            else
                btn.Enabled = false;
        }
        catch
        {
        }
    }

然而，尽管字符串与按钮的名称完全匹配，但控件 returns 为空。可以做些什么来处理这个问题？

Answer 1

试试看按钮 btn = (按钮)Table1.FindControl("btnName");

编辑：

当您在一个控件中找到一个控件时，您需要执行上述操作。

Answer 2

感谢 Matthew Watson，FindControl 在使用母版页的项目中存在问题。为了在页面中找到控件，必须首先手动向下钻取母版页及其内容：

这个：

  Button btn = FindControl(btnName) as Button;

必须采用以下格式：

  Button btn = this.Master.FindControl("MainContent").FindControl(btnName) as Button;

Answer 3

为我工作...

protected void Page_Load(object sender, EventArgs e)
{

   // txtReadyTime.Text =""; //Button will be enabled
    txtReadyTime.Text =DateTime.Now.ToShortTimeString(); //Button will be enabled
    textboxenabled(txtReadyTime);


    //Button btn = this.FindControl("btnReadyTime") as Button;
    //Title = btn.Text;
}

public void textboxenabled(TextBox box)
{
    string btnName = box.ID.Replace("txt", "btn");
    try
    {
        Button btn = FindControl(btnName) as Button;
        if (box.Text == "")
            btn.Enabled = true;
        else
            btn.Enabled = false;
    }
    catch
    {
    }
}

FindControl 返回 Null

FindControl Returning Null

c#

asp.net

null

findcontrol