在IEnumerable上使用&#39;Any&#39; <string> 在OData LINQ查询中

Question

I am using Microsoft.Data.Odata (5.6) to run following query:

IEnumerable<Service> services = context.Services.Expand(ServiceQueryExpansion)
    .Where(c =>
        (serviceNames.Any(s => s.Equals(
            c.ServiceName, StringComparison.OrdinalIgnoreCase))))

serviceNames is IEnumerable of string

I get following error while trying above query:

Error translating Linq expression to URI: The source parameter for the 'Any' method has to be either a navigation or a collection property.

How do I resolve this?

Answer 1

I know it is fun and exciting (sarcasm) but you can dynamically build your Where expression like this:

var serviceNames = new string[] { "SERVICE1","SERVICE2"};

Expression<Func<Service,bool>> inList = v => false;
var parameter = inList.Parameters[0];
var propertyExpression = Expression.Property(parameter,"ServiceName");

foreach (var serviceName in serviceNames)
{
   var body = inList.Body;
   var constantExpression = Expression.Constant(serviceName);
   var equalityExpression = Expression.Equal(propertyExpression,constantExpression);

   body = Expression.OrElse(body,equalityExpression);

   inList = Expression.Lambda<Func<Service, bool>>(body, parameter);
}

IEnumerable<Service> services = context.Services.Expand(ServiceQueryExpansion)
    .Where(inList);

This method builds a custom where clause from your list which will resemble (v => v.ServiceName == "Service1" || v.ServiceName == "Service2" || v.ServiceName == "Service3")

You could probably follow the directions from my blog http://coding.grax.com/2013/07/filter-pattern-for-linq-query-filter.html to encapsulate this logic into a custom "WhereContains(yourListHere)" custom filter extension method.

Answer 2

You could write:

var services = context.Services.Expand(ServiceQueryExpansion).AsEnumerable()
      .Where(c => serviceNames.Contains(c.ServiceName));

But it will download entire Services collection. Or:

var services = serviceNames.SelectMany(s=>
     context.Services.Expand(ServiceQueryExpansion).Where(c=> c.ServicaName == s));

That will create N requests.

I don't know any better way to do this in Linq to OData.

Answer 3

What I did was apply the filter that I could, then to list and then make another filter once you have your results locally.

var services = context.Services.Expand(ServiceQueryExpansion).ToList();
services = services.Where(s => serviceNames.Any(n => n.ServiceName.Equals(s, StringComparison.OrdinalIgnoreCase)));

This is not the best option if you have several records that you don't need to get accross the network.

Another option is to create a Data Service Operation.

[WebGet]
public IQueryable<Service> GetServicesByServiceName(string serviceNames)
{
    var serviceNamesArray = serviceNames.Split(',');
    var ctx = YourContext();
    return ctx.Services.Include("ServiceQueryExpansion").Where(s => serviceNamesArrays.Any(n => s.ServiceName.Equals(n, StringComparison.OrdinalIgnoreCase))).AsQueryable();
}