使用.Where（）的C＃实体框架过滤

Question

I am working in C# using Entity Framework and I am trying to filter a query of contacts to get all contact that have the same Id. I can get all Contacts , but I'm having issues filtering using Where . I know somethings wrong but I can't quite pinpoint it, any help would be appreciated.

See relevant code below:

public IEnumerable<model.Contact> Execute(GetContactById parameters)
{
    IEnumerable<model.Contact> ContactsById = null;

    DbRetryHandler.RetryHandler(delegate(DeviceModelContext retryContext)
    {
        ContactsById = retryContext.Contact
                    .Where(c => c.Id.equals(parameters.Id))
                    .Select(c => new model.Contact
                     {
                         // unrelated code
                     });
                });

                return ContactsById;
}

Answer 1

The provider has issues recognizing expressions it cannot translate to SQL. Try to simplify the expressions so that it can be translated to SQL more easily.

public IEnumerable<model.Contact> Execute(GetContactById parameters)
{
     IEnumerable<model.Contact> ContactsById = null;
     DbRetryHandler.RetryHandler(delegate(DeviceModelContext retryContext)
     {
         var parametersId = parameters.Id; // <-- store id in variable
         camerasByDeviceId = retryContext.Contact
           .Where(c => c.Id == parametersId) // <-- use == instead of Equals
           .Select(c => new model.Camera
           {
               // unrelated code
           });
     });

     return ContactsById;
}