WPF：无法使用FindName访问ComboBox的TextBox [英] WPF: cannot access ComboBox's TextBox with FindName

问题描述

我看到我可以访问 ComboBox （ TextBox ， PopUp 和 Button ）通过 FindName 方法。

I saw that I can access the templated parts of a ComboBox (the TextBox, PopUp and Button) via the FindName method.

应该使用 cb.FindName（ PART_EditableTextBox） TextBox 进行访问/ code>，但是这总是为我返回 null 。

The TextBox should be accessible by using cb.FindName("PART_EditableTextBox"), however, this always returns null for me.

根据melya的建议，我尝试使用 cb.Template.FindName（ PART_EditableTextBox，cb）; 代替-可以在简单的测试应用程序上使用，但不适用于我自己的应用程序。

As per melya's suggestion, I have tried using cb.Template.FindName("PART_EditableTextBox", cb); instead -- this works on a simple test app, but not my own.

也许不同之处在于，我正在尝试加载或初始化 ComboBox 之前执行此操作（我正在开发附加属性，可为 TextBoxes / ComboBoxes 添加功能。

The difference, perhaps, is that I'm trying to do this before the ComboBox is loaded or initialised (I'm developing an Attached Property that adds functionality to TextBoxes/ComboBoxes).

cb.ItemTemplate 显示为 null 。

不幸的是，尝试 cb.ApplyTemplate（）的明显解决方案返回 false 却什么也没做。

Unfortunately, the obvious solution of trying cb.ApplyTemplate() returns false and doesn't do anything.

我能做些什么吗？

推荐答案

我知道我在这里参加聚会迟到了，但是我想我会回答的话，以防其他人像我一样呆在这里。

I know I'm late to the party here, but thought I'd answer in case anyone else ends up here, like I did.

就我而言，我正在研究自定义ComboBox控件。我遵循了其他建议来在Loaded事件中处理此问题，但是（如OP）始终保持null返回。最终，我发现Loaded还为时过早。我的控件显示在最初不可见的选项卡上。

In my case, I was working on a custom ComboBox control. I followed other suggestions to handle this in the Loaded event, but (like the OP), kept getting a null return. Eventually, I figured out that Loaded was too early. My control was displayed on a tab, which was not initially visible.

相反，重写OnApplyTemplate更适合我，因为这是在Loaded事件之后（当模板可用）。我使用的代码如下：

Instead, overriding OnApplyTemplate was a better fit for me, since this comes after the Loaded event (when the template becomes available). The code I used was as follows:

public override void OnApplyTemplate()
{
    base.OnApplyTemplate();
    var textBox = Template.FindName("PART_EditableTextBox", this) as TextBox;
}

这篇关于WPF：无法使用FindName访问ComboBox的TextBox的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！