DatePicker 控件日期格式化，可以在App.xaml.cs中添加下面代码

方法一 不推荐：

Thread.CurrentThread.CurrentCulture = (CultureInfo)Thread.CurrentThread.CurrentCulture.Clone();

Thread.CurrentThread.CurrentCulture.DateTimeFormat.ShortDatePattern = "yyyy-MM-dd";

方法二：

I have solved this problem with a help of this code. Hope it will help you all as well.

<Style TargetType="{x:Type DatePickerTextBox}">

 <Setter Property="Control.Template">

  <Setter.Value>

   <ControlTemplate>

    <TextBox x:Name="PART_TextBox"

     Text="{Binding Path=SelectedDate, StringFormat='dd MMM yyyy',

     RelativeSource={RelativeSource AncestorType={x:Type DatePicker}}}" />

   </ControlTemplate>

  </Setter.Value>

 </Setter>

</Style>

方法三：
Converter class:

public class DateFormat : IValueConverter

{

    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)

    {

        if (value == null) return null;

        return ((DateTime)value).ToString("dd-MMM-yyyy");

    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)

    {

        throw new NotImplementedException();

    }

}

WPF tag

<DatePicker Grid.Column="3" SelectedDate="{Binding DateProperty, Converter={StaticResource DateFormat}}" Margin="5"/>

FileHelper.cs

#region 01.读取文件方法 —— static string ReadFile(string path)
/// <summary>
/// 读取文件方法
/// </summary>
/// <param name="path">路径</param>
/// <returns>内容字符串</returns>
/// <exception cref="ArgumentNullException">路径为空</exception>
public static string ReadFile(string path)
{
#region # 验证参数

if (string.IsNullOrWhiteSpace(path))
{
throw new ArgumentNullException(nameof(path), @"路径不可为空！");
}

#endregion

StreamReader reader = null;

try
{
reader = new StreamReader(path, Encoding.UTF8);
string content = reader.ReadToEnd();
return content;
}
finally
{
reader?.Dispose();
}
}
#endregion

#region 02.写入文件方法 —— static void WriteFile(string path, string content)
/// <summary>
/// 写入文件方法
/// </summary>
/// <param name="path">路径</param>
/// <param name="content">内容</param>
/// <param name="append">是否附加</param>
/// <exception cref="ArgumentNullException">路径为空</exception>
public static void WriteFile(string path, string content, bool append = false)
{
#region # 验证参数

if (string.IsNullOrWhiteSpace(path))
{
throw new ArgumentNullException(nameof(path), "路径不可为空！");
}

#endregion

FileInfo file = new FileInfo(path);
StreamWriter writer = null;

if (file.Exists && !append)
{
file.Delete();
}
try
{
//获取文件目录并判断是否存在
string directory = Path.GetDirectoryName(path);

if (string.IsNullOrEmpty(directory))
{
throw new ArgumentNullException(nameof(path), "目录不可为空！");
}
if (!Directory.Exists(directory))
{
Directory.CreateDirectory(directory);
}

writer = append ? file.AppendText() : new StreamWriter(path, false, Encoding.UTF8);
writer.Write(content);
}
finally
{
writer?.Dispose();
}
}
#endregion

JsonHelper.cs

/// <summary>
/// JSON辅助操作类
/// </summary>
public static class JsonHelper
{
/// <summary>
/// 处理Json的时间格式为正常格式
/// </summary>
public static string JsonDateTimeFormat(string json)
{
json = Regex.Replace(json,
@"\\/Date\((\d+)\)\\/",
match =>
{
var dt = new DateTime(1970, 1, 1);
dt = dt.AddMilliseconds(long.Parse(match.Groups[1].Value));
dt = dt.ToLocalTime();
return dt.ToString("yyyy-MM-dd HH:mm:ss.fff");
});
return json;
}

/// <summary>
/// 把对象序列化成Json字符串格式
/// </summary>
/// <param name="object"></param>
/// <returns></returns>
public static string ToJson(object @object)
{
var json = JsonConvert.SerializeObject(@object);
return JsonDateTimeFormat(json);
}

/// <summary>
/// 把Json字符串转换为强类型对象
/// </summary>
public static T FromJson<T>(string json)
{
json = JsonDateTimeFormat(json);
return JsonConvert.DeserializeObject<T>(json);
}
}

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