wpf通过控件名查找控件

介绍 (Introduction)

在开发Web应用程序时，单个页面可能包含许多区域，每个区域可能包含许多具有执行回发功能的控件。 很多时候，您可能需要根据导致回发发生的控件对ASP.NET回发执行一些操作。 例如，该操作可能是将焦点重新设置到导致回发的控件上，或者将其他控件加载到导致回发的控件上。

In this article, we will look into the JavaScript __doPostBack function and then as a little walkthrough we will write one small program to determine the control that causes the postback

在本文中，我们将研究JavaScript

Let us take a look at the __doPostBack function shown below:

让我们看一下下面显示的__doPostBack函数：

function __doPostBack(eventTarget, eventArgument) {
   if (!theForm.onsubmit || (theForm.onsubmit() != false)) {
   theForm.__EVENTTARGET.value = eventTarget;theForm.__EVENTARGUMENT.value = eventArgument;theForm.submit();}}

The __doPostBack function takes two arguments eventTarget, and eventArgument. The eventTarget contains the ID of the control that causes the postback and the eventArgument contains any additional data associated with the control. One thng should be noted that the two hidden fields _EVENTTARGET and _EVENTARGUMENT are automatically declared. the value of the eventTarget and eventArgument are stored in the hidden fields. The two hidden variables can be accessed from code behind using the forms/params collection.

__doPostBack函数采用两个参数eventTarget和eventArgument。 和

查找导致PostBack的控件： (Finding the control that caused the PostBack:)

您可以使用以下代码从表单参数集合中检索_EVENTTARGET隐藏变量的值，从而找到引起回发的控件的ID：

protected void Page_Load(object sender, EventArgs e)        {
               string controlName = Request.Params.Get("__EVENTTARGET");            Response.Write("control caused the postback is: " + controlName);        }

尝试使上面的代码起作用： (Try putting the above code to work:)

1个 (1)

在页面上添加三个DropDownList控件，并将所有三个控件的AutoPostBack属性设置为true。 保留所有控件的默认ID，即DropDownList1，DropDownList2，DropDownList3。

2 (2)

用一些伪数据填充每个dropdownlist控件。

3 (3)

在Page_Load事件中编写以下代码。

protected void Page_Load(object sender, EventArgs e)        {
               string controlName = Request.Params.Get("__EVENTTARGET");            Response.Write("control caused the postback is: " + controlName);        }

4 (4)

运行代码以验证输出程序将显示导致回发的controlName。 如果查看页面的源代码，则可以看到DropDownList的onchange事件调用__doPostBack函数。 控件 DropDownList1DropDownList1

忙于处理按钮和图像按钮的回发 (Wroking with Buttons and ImageButtons to Handle Postbacks)

If you see the code generated by Button (or ImageButton) <input type="submit" name="Button1" value="Do PostBack" id="Button1" /> the button control (or the ImageButton control) does not call the __doPostBack function, and hence the _EVENTTARGET will always be empty. However, you can findout the ID of the Button by looping through the form controls collection.

如果您看到由Button（或ImageButton）生成的代码<input type =“ submit” name =“ Button1” value =“ Do PostBack” id =“ Button1” />，则按钮控件（或ImageButton控件）不会调用__doPostBack函数，因此_EVENTTARGET始终为空。 但是，您可以通过遍历表单控件集合来找到Button的ID。

I have written one small function GetPostBackControl that returns control name as string datatype that caused the postback. All the statements inside the function are self explanatory. Comments have been included where-ever necessary.

我编写了一个小函数

试试看： (Try it out:)

1个 (1)

在页面上添加不同的控件，例如DropDownLists，CheckBoxes，Buttons。 对于DropDownLists或CheckBoxes，请将AutoPostBack属性设置为true。 我在页面中添加了三个DropDownLists，四个Button和三个CheckBox。 相应的.ASPX代码如下所示：

    
    
    
     
        
                  
       
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2 (2)

在代码隐藏页面中编写以下函数：

public string GetPostBackControl(Page page)        {
               string controlName = page.Request.Params.Get("__EVENTTARGET");            if (controlName == string.Empty)            {
                   //Means,  some Button or ImageButton has been clicked.                foreach (string controlItem in page.Request.Form)                {
                       Control c = Page.FindControl(controlItem);                    if (c is Button)                    {
                           controlName = c.ID;                        break;                    }                }            }            return controlName;        }

3 (3)

To use the above function, write the following code in the Page_Load event:

若要使用上述功能，请在Page_Load事件中编写以下代码：

protected void Page_Load(object sender, EventArgs e)        {
               string control = GetPostBackControl(this.Page);            Response.Write("Control caused postback:" + control);        }

4 (4)

现在，运行上面的代码，并检查导致回发的控件。

Hope this article helps to all the readers. Happy programming!

希望本文对所有读者有所帮助。 编程愉快！

翻译自:

wpf通过控件名查找控件