c# – ASP.NET MVC Web API并传递oData查询

发布时间：2020-12-15 21:55:07 所属栏目：百科来源：网络整理

导读：我目前正在使用oData过滤器请求执行Web API,如下所示： public IQueryableOrganizationViewModel Get(ODataQueryOptionsOrganization oDataQuery){ var query = new FindOrganizationsQuery(oDataQuery); var result =_findOrganizationsQueryHandler.Execut

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 });
}

处理程序看起来像：

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

查询类看起来像：

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oData过滤器,它处理得很好,这一切都正常.

但是现在,我不想将类型ODataQueryOptions传递给Get操作,而是希望有FindOrganizationsQuery类,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,我如何传递oData过滤器？

解决方法

您可以为我们为ODataQueryOptions执行的 same way的FindOrganizationsQuery编写自定义参数绑定属性,然后使用该属性对FindOrganizationsQuery进行属性.

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);
        }
    }
}

我从web API源代码复制的扩展方法因为它不公开.

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;
    }
}

我有完整的样品here.

（编辑：李大同）

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