Question

怎么设置WPF的DatePicker默认显示“请选择一个日期”

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

/// <summary>
/// 递归寻找指定名称和指定类型的控件(辅助方法)
/// </summary>
/// <typeparam name="T">寻找的类型</typeparam>
/// <param name="reference">对象</param>
/// <param name="controlName">需要寻找的控件名称</param>
/// <param name="maxLevel">最大递归级数</param>
/// <param name="currentLevel">当前已经递归的级数</param>
/// <returns>返回寻找的类型</returns>
public static T RecursionFindControl<T>(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<T>(obj, controlName, maxLevel, currentLevel + 1) as DependencyObject;
if (obj != null)
{
return obj as T;
}
}
}
}

return obj as T;
}
}

Answer 2

不知道是extjs的dataPicker还是jquery插件的 extjs: { xtype: 'datafiled', value: new Date() } jquery插件 $("#datepicker").datepicker( { defaultDate : new Date() //还可以是时间字符串，当前日期对应的时间数值 } );