c# - ASP.NET MVC Web API和传递oData查询

我目前正在使用oData过滤器请求执行Web API，如下所示：

public IQueryable<OrganizationViewModel> Get(ODataQueryOptions<Organization> oDataQuery)
{
    var query = new FindOrganizationsQuery(oDataQuery);
    var result =_findOrganizationsQueryHandler.Execute(query);
    return result.Organizations.Select(o => new OrganizationViewModel { Id = o.PublicId, Name = o.Name });
}

该处理程序如下所示：

public FindOrganizationsQueryResult Execute(FindOrganizationsQuery request)
{
    var organizations = request.ODataQuery.ApplyTo(_mgpQueryContext.Organizations).Cast<Organization>();
    return new FindOrganizationsQueryResult(organizations);
}

查询类如下所示：

public class FindOrganizationsQuery
{
    public FindOrganizationsQuery(ODataQueryOptions<Organization> oDataQuery)
    {
        ODataQuery = oDataQuery;
    }
    public ODataQueryOptions<Organization> ODataQuery { get; set; }
}

因此，如果我通过请求传递了oData过滤器，则可以很好地处理它，并且一切正常。

但是现在，我没有将ODataQueryOptions类型传递给Get操作，而是希望使用FindOrganizationsQuery类，例如：

public IQueryable<OrganizationViewModel> FindOrganizations(FindOrganizationsQuery query)
{
    // query is null
}

但是，查询参数始终为null。如果ODataQueryOptions参数在另一个类中，如何通过oData过滤器？

最佳答案

您可以为FindOrganizationsQuery编写same way的自定义参数绑定属性，然后为ODataQueryOptions编写here，然后为该FindOrganizationsQuery赋予该属性。

下面是一些示例代码，

public class CustomQueryBindingAttribute : ParameterBindingAttribute
{
    public override HttpParameterBinding GetBinding(HttpParameterDescriptor parameter)
    {
        return new CustomQueryBinding(parameter);
    }

    internal class CustomQueryBinding : HttpParameterBinding
    {
        public CustomQueryBinding(HttpParameterDescriptor parameter)
            : base(parameter)
        {
        }

    internal class CustomQueryBinding : HttpParameterBinding
    {
        public CustomQueryBinding(HttpParameterDescriptor parameter)
            : base(parameter)
        {
        }

        public override Task ExecuteBindingAsync(ModelMetadataProvider metadataProvider,
            HttpActionContext actionContext, CancellationToken cancellationToken)
        {
            IEdmModel model = actionContext.Request.GetEdmModel() ?? actionContext.ActionDescriptor.GetEdmModel(typeof(Organization));
            ODataQueryContext queryContext = new ODataQueryContext(model, typeof(Organization));

            object customQuery = CreateCustomQuery(queryContext, actionContext.Request);
            SetValue(actionContext, customQuery);

            return Task.FromResult(0);
        }

        private object CreateCustomQuery(ODataQueryContext queryContext, HttpRequestMessage request)
        {
            Type parameterType = Descriptor.ParameterType;
            // Assuming all custom queries have this public property.
            Type oDataQueryOptionsOfTType = parameterType.GetProperty("ODataQuery").PropertyType;

            object odataQueryOptions = Activator.CreateInstance(oDataQueryOptionsOfTType, queryContext, request);
            return Activator.CreateInstance(parameterType, odataQueryOptions);
        }
    }
}

以及我从Web API源代码复制的扩展方法，因为它不是公开的。

public static class HttpActionDescriptorExtensions
{
    internal const string EdmModelKey = "MS_EdmModel";

    internal static IEdmModel GetEdmModel(this HttpActionDescriptor actionDescriptor, Type entityClrType)
    {
        // save the EdmModel to the action descriptor
        return actionDescriptor.Properties.GetOrAdd(EdmModelKey + entityClrType.FullName, _ =>
        {
            ODataConventionModelBuilder builder = new ODataConventionModelBuilder(actionDescriptor.Configuration, isQueryCompositionMode: true);
            EntityTypeConfiguration entityTypeConfiguration = builder.AddEntity(entityClrType);
            builder.AddEntitySet(entityClrType.Name, entityTypeConfiguration);
            IEdmModel edmModel = builder.GetEdmModel();
            return edmModel;
        }) as IEdmModel;
    }
}

我有完整的样本。