我正在使用EntitySetController创建一个oData web api控制器,除了获取总记录数之外,一切运行良好.
@H_403_2@控制器定义如下：
检测到无效操作. ‘$count’不是可以绑定到’Collection([Entity1 Nullable = False])’的动作.
public class MyODataController : EntitySetController<Entity1,int> where TEntity : class
{
public override IQueryable<Entity1> Get()
{
return EntityDatabase.Get();
}
}
@H_403_2@当我打电话给我时：
http://localhost:44789/oData/MyOData/$count@H_403_2@我收到错误：
检测到无效操作. ‘$count’不是可以绑定到’Collection([Entity1 Nullable = False])’的动作.
解决方法
不幸的是,虽然Web API在未来的版本中应该是开箱即用,但它并不支持$count开箱即用.在此期间,您仍然可以通过定义这些类来添加支持：
public class CountODataRoutingConvention : EntitySetRoutingConvention
{
public override string SelectAction(ODataPath odataPath,HttpControllerContext controllerContext,ILookup<string,HttpActionDescriptor> actionMap)
{
if (controllerContext.Request.Method == HttpMethod.Get && odataPath.PathTemplate == "~/entityset/$count")
{
if (actionMap.Contains("GetCount"))
{
return "GetCount";
}
}
return null;
}
}
public class CountODataPathHandler : DefaultODataPathHandler
{
protected override ODataPathSegment ParseAtEntityCollection(IEdmModel model,ODataPathSegment prevIoUs,IEdmType prevIoUsEdmType,string segment)
{
if (segment == "$count")
{
return new CountPathSegment();
}
return base.ParseAtEntityCollection(model,prevIoUs,prevIoUsEdmType,segment);
}
}
public class CountPathSegment : ODataPathSegment
{
public override string SegmentKind
{
get
{
return "$count";
}
}
public override IEdmType GetEdmType(IEdmType prevIoUsEdmType)
{
return EdmCoreModel.Instance.FindDeclaredType("Edm.Int32");
}
public override IEdmEntitySet GetEntitySet(IEdmEntitySet prevIoUsEntitySet)
{
return prevIoUsEntitySet;
}
public override string ToString()
{
return "$count";
}
}
@H_403_2@在MapODataRoute中注册它们：
IList<IODataRoutingConvention> routingConventions = ODataRoutingConventions.CreateDefault();
routingConventions.Insert(0,new CountODataRoutingConvention());
config.Routes.MapODataRoute("OData","odata",GetModel(),new CountODataPathHandler(),routingConventions);
@H_403_2@在您的控制器中,添加此方法：
public HttpResponseMessage GetCount(ODataQueryOptions<TEntity> queryOptions)
{
IQueryable<TEntity> queryResults = queryOptions.ApplyTo(Get()) as IQueryable<TEntity>;
int count = queryResults.Count();
HttpResponseMessage response = new HttpResponseMessage(HttpStatusCode.OK);
response.Content = new StringContent(count.ToString(),Encoding.UTF8,"text/plain");
return response;
}
@H_403_2@为了避免将GetCount()复制到每个控制器,您可以定义一个从定义GetCount的EntitySetController派生的基类.
