web api 2，odata v4，ConcurrencyCheck发出错误响应。

Question

我的模型

public abstract class BaseEntit 
{ 
    public DateTime rowCreatedDT { get; set; }  
    public DateTime rowLastModifiedDT { get; set; }  
    public int user_id1 { get; set; }  
    public int user_id2 { get; set; } 
} 
[Table("ab")] 
public class Ab : BaseEntit 
{ 
    [Key] 
    public int id { get; set; } 
    public string name { get; set; }   
} 

配置

public static IEdmModel GetModel() 
{ 
     ODataModelBuilder builder = new ODataConventionModelBuilder(); 
     var myEntity = builder.EntitySet<Ab>("abs");    
     return builder.GetEdmModel(); 
} 
public static void Register(HttpConfiguration config) 
{ 
    //config.EnableCors();   
    config.MessageHandlers.Add(new AuthenticationHandler()); 
    config.MapHttpAttributeRoutes(); 
    config.AddODataQueryFilter(); 
    config.Filters.Add(new NotImplExceptionFilterAttribute()); 
    config.MapODataServiceRoute("odata", "api", GetModel()); 
} 

控制器

[ODataRoutePrefix("abs")] 
public class AbController : ODataController 
{ 
    protected DB db = new DB(); 
    protected override void Dispose(bool disposing) 
    { 
     db.Dispose(); 
     base.Dispose(disposing); 
    } 
    [ODataRoute("")] 
    [EnableQuery] 
    public IQueryable<Ab> get() 
    { 
     try 
     { 
      return db.abs; 
     } 
     catch (Exception ex) 
     { 
      throw ex; 
     } 
    } 
} 

上面的代码工作正常。但是当我添加一个ConcurrencyCheck时，我得到一个错误响应。我做错了什么？ （如果我使用ApiController不是OData，它也可以正常工作） 还有一个问题，我该如何捕获异常？我正在使用vs2012。

public abstract class BaseEntit 
{ 
    public DateTime rowCreatedDT { get; set; } 
    [ConcurrencyCheck] //<-- add here 
    public DateTime rowLastModifiedDT { get; set; }  
    public int user_id1 { get; set; }  
    public int user_id2 { get; set; } 
} 

Answer 1

是的。到目前为止，DateTime属性不支持ETag。这里是相应的github issue。

但是，您可以解决的：

1.创建自己的ETAGE Handlder。

例如：

public class MyODataEtagHanlder : IETagHandler 
{ 
private const string NullLiteralInETag = "null"; 

private const char Separator = ','; 

public TimeZoneInfo TimeZone { get; set; } 

public EntityTagHeaderValue CreateETag(IDictionary<string, object> properties) 
{ 
    if (properties.Count == 0) 
    { 
     return null; 
    } 

    StringBuilder builder = new StringBuilder(); 
    builder.Append('\"'); 
    bool firstProperty = true; 

    foreach (object propertyValue in properties.OrderBy(p => p.Key).Select(p => p.Value)) 
    { 
     if (firstProperty) 
     { 
      firstProperty = false; 
     } 
     else 
     { 
      builder.Append(Separator); 
     } 

     string str; 
     if (propertyValue is DateTime) 
     { 
      str = GetUriRepresentationForDateTime((DateTime)propertyValue, TimeZone); 
     } 
     else 
     { 
      str = ODataUriUtils.ConvertToUriLiteral(propertyValue, ODataVersion.V4); 
     } 

     // base64 encode 
     byte[] bytes = Encoding.UTF8.GetBytes(str); 
     string etagValueText = Convert.ToBase64String(bytes); 
     builder.Append(etagValueText); 
    } 

    builder.Append('\"'); 
    string tag = builder.ToString(); 
    return new EntityTagHeaderValue(tag, isWeak: true); 
} 

public IDictionary<string, object> ParseETag(EntityTagHeaderValue etagHeaderValue) 
{ 
    string tag = etagHeaderValue.Tag.Trim('\"'); 

    // split etag 
    string[] rawValues = tag.Split(Separator); 
    IDictionary<string, object> properties = new Dictionary<string, object>(); 
    for (int index = 0; index < rawValues.Length; index++) 
    { 
     string rawValue = rawValues[index]; 

     // base64 decode 
     byte[] bytes = Convert.FromBase64String(rawValue); 
     string valueString = Encoding.UTF8.GetString(bytes); 
     object obj = ODataUriUtils.ConvertFromUriLiteral(valueString, ODataVersion.V4); 

     properties.Add(index.ToString(CultureInfo.InvariantCulture), obj); 
    } 

    return properties; 
} 

public static string GetUriRepresentationForDateTime(DateTime dateTime, TimeZoneInfo timeZoneInfo) 
{ 
    object value = ConvertUnsupportedDateTime(dateTime, timeZoneInfo); 
    return ODataUriUtils.ConvertToUriLiteral(value, ODataVersion.V4); 
} 

internal static DateTimeOffset ConvertUnsupportedDateTime(DateTime value, TimeZoneInfo timeZoneInfo) 
{ 
    if (timeZoneInfo == null) 
    { 
     timeZoneInfo = TimeZoneInfo.Local; 
    } 

    if (value.Kind == DateTimeKind.Utc || value.Kind == DateTimeKind.Local) 
    { 
     return new DateTimeOffset(value.ToUniversalTime()).ToOffset(timeZoneInfo.BaseUtcOffset); 
    } 

    DateTimeOffset dateTimeOffset = new DateTimeOffset(value, timeZoneInfo.GetUtcOffset(value)); 
    return dateTimeOffset.ToUniversalTime().ToOffset(timeZoneInfo.BaseUtcOffset); 
} 
} 

2.配置ETag的处理

MyODataEtagHandler etagHandler = new MyODataEtagHandler(); 
etagHandler.TimeZone = TimeZoneInfo.Local; 
config.SetETagHandler(etagHandler); 
config.MapODataServiceRoute("odata", "api", GetModel()); 

3.然后你就可以查询实体集。

例如：

{ 
    "@odata.context":"http://localhost/api/$metadata#abs","value":[ 
    { 
     "@odata.etag":"W/\"MjAxNS0wMi0xNVQxMTozMDo1NC41ODU3MTc1KzA4OjAw\"","id":1, 
"name":"ab #1","rowCreatedDT":"2015-02-15T11:30:54.5857175+08:00","rowLastModifi 
edDT":"2015-02-15T11:30:54.5857175+08:00","user_id1":11,"user_id2":21 
    },{ 
     "@odata.etag":"W/\"MjAxNS0wMi0xNVQxMTozMDo1NC41ODU3MTc1KzA4OjAw\"","id":2, 
"name":"ab #2","rowCreatedDT":"2015-02-15T11:30:54.5857175+08:00","rowLastModifi 
edDT":"2015-02-15T11:30:54.5857175+08:00","user_id1":12,"user_id2":22 
    },{ 
     "@odata.etag":"W/\"MjAxNS0wMi0xNVQxMTozMDo1NC41ODU3MTc1KzA4OjAw\"","id":3, 
"name":"ab #3","rowCreatedDT":"2015-02-15T11:30:54.5857175+08:00","rowLastModifi 
edDT":"2015-02-15T11:30:54.5857175+08:00","user_id1":13,"user_id2":23 
    },{ 
     "@odata.etag":"W/\"MjAxNS0wMi0xNVQxMTozMDo1NC41ODU3MTc1KzA4OjAw\"","id":4, 
"name":"ab #4","rowCreatedDT":"2015-02-15T11:30:54.5857175+08:00","rowLastModifi 
edDT":"2015-02-15T11:30:54.5857175+08:00","user_id1":14,"user_id2":24 
    },{ 
     "@odata.etag":"W/\"MjAxNS0wMi0xNVQxMTozMDo1NC41ODU3MTc1KzA4OjAw\"","id":5, 
"name":"ab #5","rowCreatedDT":"2015-02-15T11:30:54.5857175+08:00","rowLastModifi 
edDT":"2015-02-15T11:30:54.5857175+08:00","user_id1":15,"user_id2":25 
    } 
    ] 
} 

谢谢。