我们的解决方案第 1 部分：实体框架
当实体框架DateTime从数据库中获取值时，它会将它们设置为DateTimeKind.Unspecified. 换句话说，既不是本地的也不是UTC。我们特别想将我们的日期标记为DateTimeKind.Local.
为了实现这一点，我们决定调整生成实体类的实体框架模板。我们没有将日期作为一个简单的属性，而是引入了一个后备存储日期，并使用属性设置器来设置日期（Local如果它是Unspecified.
在模板（.tt 文件）中，我们替换了...
public string Property(EdmProperty edmProperty)
{
return string.Format(
CultureInfo.InvariantCulture,
"{0} {1} {2} {{ {3}get; {4}set; }}",
Accessibility.ForProperty(edmProperty),
_typeMapper.GetTypeName(edmProperty.TypeUsage),
_code.Escape(edmProperty),
_code.SpaceAfter(Accessibility.ForGetter(edmProperty)),
_code.SpaceAfter(Accessibility.ForSetter(edmProperty)));
}
... 和 ...
public string Property(EdmProperty edmProperty)
{
// Customised DateTime property handler to default DateKind to local time
if (_typeMapper.GetTypeName(edmProperty.TypeUsage).Contains("DateTime")) {
return string.Format(
CultureInfo.InvariantCulture,
"private {1} _{2}; {0} {1} {2} {{ {3}get {{ return _{2}; }} {4}set {{ _{2} = DateKindHelper.DefaultToLocal(value); }}}}",
Accessibility.ForProperty(edmProperty),
_typeMapper.GetTypeName(edmProperty.TypeUsage),
_code.Escape(edmProperty),
_code.SpaceAfter(Accessibility.ForGetter(edmProperty)),
_code.SpaceAfter(Accessibility.ForSetter(edmProperty)));
} else {
return string.Format(
CultureInfo.InvariantCulture,
"{0} {1} {2} {{ {3}get; {4}set; }}",
Accessibility.ForProperty(edmProperty),
_typeMapper.GetTypeName(edmProperty.TypeUsage),
_code.Escape(edmProperty),
_code.SpaceAfter(Accessibility.ForGetter(edmProperty)),
_code.SpaceAfter(Accessibility.ForSetter(edmProperty)));
}
}
这创建了一个相当丑陋的单行设置器，但它完成了工作。它确实使用辅助函数将日期默认为Local如下所示：
public class DateKindHelper
{
public static DateTime DefaultToLocal(DateTime date)
{
return date.Kind == DateTimeKind.Unspecified ? DateTime.SpecifyKind(date, DateTimeKind.Local) : date;
}
public static DateTime? DefaultToLocal(DateTime? date)
{
return date.HasValue && date.Value.Kind == DateTimeKind.Unspecified ? DateTime.SpecifyKind(date.Value, DateTimeKind.Local) : date;
}
}
我们的解决方案第 2 部分：IQueryable 过滤器
where下一个问题是 Breeze 在将子句应用于我们的IQueryable控制器操作时传递 UTC 日期。在审查了 Breeze、Web API 和实体框架的代码后，我们决定最好的选择是拦截对我们控制器操作的调用，并将 UTC 日期替换为QueryString本地日期。
我们选择使用可以应用于控制器操作的自定义属性来执行此操作，例如：
[UseLocalTime]
public IQueryable<Product> Products()
{
return _dc.Context.Products;
}
实现此属性的类是：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Http;
using System.Web.Http.Filters;
using System.Text.RegularExpressions;
using System.Xml;
namespace TestBreeze.Controllers.api
{
public class UseLocalTimeAttribute : ActionFilterAttribute
{
Regex isoRegex = new Regex(@"((?:-?(?:[1-9][0-9]*)?[0-9]{4})-(?:1[0-2]|0[1-9])-(?:3[0-1]|0[1-9]|[1-2][0-9])T(?:2[0-3]|[0-1][0-9]):(?:[0-5][0-9]):(?:[0-5][0-9])(?:\.[0-9]+)?Z)", RegexOptions.IgnoreCase);
public override void OnActionExecuting(System.Web.Http.Controllers.HttpActionContext actionContext)
{
// replace all ISO (UTC) dates in the query string with local dates
var uriString = HttpUtility.UrlDecode(actionContext.Request.RequestUri.OriginalString);
var matches = isoRegex.Matches(uriString);
if (matches.Count > 0)
{
foreach (Match match in matches)
{
var localTime = XmlConvert.ToDateTime(match.Value, XmlDateTimeSerializationMode.Local);
var localString = XmlConvert.ToString(localTime, XmlDateTimeSerializationMode.Local);
var encoded = HttpUtility.UrlEncode(localString);
uriString = uriString.Replace(match.Value, encoded);
}
actionContext.Request.RequestUri = new Uri(uriString);
}
base.OnActionExecuting(actionContext);
}
}
}
我们的解决方案第 3 部分：Json
这可能更具争议性，但我们的网络应用程序受众也完全是本地的 :)。
我们希望发送给客户端的 Json 默认包含本地时区的日期/时间。此外，我们希望从客户端收到的任何 Json 日期都转换为我们的本地时区。为此，我们创建了一个自定义JsonLocalDateTimeConverter并更换了 Json 转换器 Breeze 安装。
转换器如下所示：
public class JsonLocalDateTimeConverter : IsoDateTimeConverter
{
public JsonLocalDateTimeConverter () : base()
{
// Hack is for the issue described in this post (copied from BreezeConfig.cs):
// http://stackoverflow.com/questions/11789114/internet-explorer-json-net-javascript-date-and-milliseconds-issue
DateTimeFormat = "yyyy-MM-dd\\THH:mm:ss.fffK";
}
// Ensure that all dates go out over the wire in full LOCAL time format (unless date has been specifically set to DateTimeKind.Utc)
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
if (value is DateTime)
{
// if datetime kind is unspecified then treat is as local time
DateTime dateTime = (DateTime)value;
if (dateTime.Kind == DateTimeKind.Unspecified)
{
dateTime = DateTime.SpecifyKind(dateTime, DateTimeKind.Local);
}
base.WriteJson(writer, dateTime, serializer);
}
else
{
base.WriteJson(writer, value, serializer);
}
}
// Ensure that all dates arriving over the wire get parsed into LOCAL time
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
var result = base.ReadJson(reader, objectType, existingValue, serializer);
if (result is DateTime)
{
DateTime dateTime = (DateTime)result;
if (dateTime.Kind != DateTimeKind.Local)
{
result = dateTime.ToLocalTime();
}
}
return result;
}
}
最后为了安装上面的转换器，我们创建了一个CustomBreezeConfig类：
public class CustomBreezeConfig : Breeze.WebApi.BreezeConfig
{
protected override JsonSerializerSettings CreateJsonSerializerSettings()
{
var baseSettings = base.CreateJsonSerializerSettings();
// swap out the standard IsoDateTimeConverter that breeze installed with our own
var timeConverter = baseSettings.Converters.OfType<IsoDateTimeConverter>().SingleOrDefault();
if (timeConverter != null)
{
baseSettings.Converters.Remove(timeConverter);
}
baseSettings.Converters.Add(new JsonLocalDateTimeConverter());
return baseSettings;
}
}
就是这样。欢迎所有意见和建议。