怎么设置WPF的DatePicker默认显示“请选择一个日期”

2025-04-05 19:39:06

推荐回答（1个）

回答1：

可以,方法有2种,一种是用代码,一种是重写样式,我来演示一下用代码怎么实现

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//首先在你的App类,即创建项目的时候App.xaml下的类
public partial class App : Application
{
//在启动方法中为时间控件注册一个加载事件
void app_Startup(object sender,StartupEventArgs e)
{

EventManager.RegisterClassHandler(typeof(DatePicker),
FrameworkElement.LoadedEvent,
new RoutedEventHandler(DatePicker_Loaded));
}
void DatePicker_Loaded(object sender, RoutedEventArgs e)
{
var dp = sender as DatePicker;
if (dp == null) return;

var wm = RecursionFindControl(dp, "PART_Watermark");
if (wm == null) return;
//重新默认水印值
wm.Content = "请选择一个日期";
}

///

/// 递归寻找指定名称和指定类型的控件(辅助方法)
///

/// 寻找的类型
/// 对象
/// 需要寻找的控件名称
/// 最大递归级数
/// 当前已经递归的级数
/// 返回寻找的类型
public static T RecursionFindControl(DependencyObject reference, string controlName = "", int maxLevel = int.MaxValue, int currentLevel = 1) where T : class
{
DependencyObject obj = null;
if (reference == null)
{
return obj as T;
}
for (int i = 0; i < VisualTreeHelper.GetChildrenCount(reference); i++)
{
obj = VisualTreeHelper.GetChild(reference, i);
FrameworkElement elemnt = obj as FrameworkElement;
if (elemnt == null)
{
break;
}

if (elemnt is T &&
((!string.IsNullOrEmpty(controlName)
&& elemnt.Name == controlName)
|| string.IsNullOrEmpty(controlName)))
{
return obj as T;
}
else
{
if (currentLevel < maxLevel)//递归层级限制
{
obj = RecursionFindControl(obj, controlName, maxLevel, currentLevel + 1) as DependencyObject;
if (obj != null)
{
return obj as T;
}
}
}
}

return obj as T;
}
}