'Double DistanceBetween..' cannot be translated into a LINQ to Expression

flyinhawaiian · October 13th, 2010, 09:41 AM

Page 140
I got a runtime error when search is pressed. Doesn't appear that anyone else has this problem or maybe just unreported.

Error:
base {System.SystemException} = {"The specified method 'Double DistanceBetween(Double, Double, Double, Double)' on the type
'NerdDinner.Models.DinnerRepository' cannot be translated into a LINQ to Entities store expression."}

Traced the problem to Code Snippet 1-99.txt

DinnerRepository.cs
Change this:
[EdmFunction("NerdDinnerModel.Store", "DistanceBetween")]

To this:

Code:

[EdmFunction("NerdDinner.Models.Store", "DistanceBetween")]

Note on Page 24, Figure 1-46 shows Model Namespace: NerdDinner.Models.

ajameson · October 16th, 2010, 07:29 AM

Something else that needs sorted on the FindByLocation() method is the lambda expression.

Code:

var dinners = from dinner in FindUpcomingDinners()
              join i in NearestDinners(latitude, longitude)
              on dinner.DinnerID equals i.DinnerID
              select dinner;

Will highlight an error on

Code:

NearestDinners(latitude, longitude)

unless you include the following method (in the downloaded final solution this method is included immediately below the public static double DistanceBetween() stub function in DinnerRepository.cs)

Code:

public IQueryable<Dinner> NearestDinners(double latitude, double longitude)
{
    return from d in entities.Dinners
           where DistanceBetween(latitude, longitude, d.Latitude, d.Longitude) < 100
           select d;
}

ethan.kapua · October 29th, 2010, 04:56 PM

@flyinhawaiian

Did you ever find an answer to your problem? I am having the same issue as well and I can't believe nobody else has posted this problem.

flyinhawaiian · October 29th, 2010, 07:05 PM

Yea, I answered my own problem.

Change this:
[EdmFunction("NerdDinnerModel.Store", "DistanceBetween")]

To this:

Code:

[EdmFunction("NerdDinner.Models.Store", "DistanceBetween")]

Notice the period between NerdDinner and Models. I think I may have done some other adjustments found in the forum (search for "NearestDinners"). Continue to post messages in the forums if you still have problems. I'll try to help you get through.

ethan.kapua · October 29th, 2010, 08:03 PM

@flyinHawaiian

Thanks for the tip! I needed to adjust the Json Object to return an EventDate to get it to fully work, but now it does! So what is going on here? We are referencing where the NerdDinner.edmx is through NerDinner.Models and then the added .Store at the end references where the DistanceBetween function is?

Thanks again. I may ask you for more help as I go along!

flyinhawaiian · October 29th, 2010, 08:19 PM

@ethan
Yes, it's called the namespace. The book fumbled on this (and many other things). You'll see namespaces used everywhere classes are defined. Often you can have more than one class with the same name. They can coexist because each can be in their own namespace. Namespaces help distinguish one class from another. Just like you can have two peopled named Kimo. One that lives on Maui and the other on Oahu. I'm monitoring all the threads. So, I'll see whatever is posted in the forum for ASP.net MVC.

alvicstep · October 17th, 2011, 04:54 PM

In my case I had to update DistanceBetween function in the edmx file:

<Function Name="DistanceBetween" ReturnType="float" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="true" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo">
<Parameter Name="Lat1" Type="float" Mode="In" />
<Parameter Name="Long1" Type="float" Mode="In" />
<Parameter Name="Lat2" Type="float" Mode="In" />
<Parameter Name="Long2" Type="float" Mode="In" />
</Function>

All parameters and a return type should be float

mengxiao88 · June 18th, 2012, 11:51 PM

you may have to change the datatype of the properties of Latitude and Longtitude in NerdDinner.Design.CS
public global::System.Double Latitude{....}
private global::System.Double _Latitude;
public global::System.Double Longitude{....}
private global::System.Double _Longitude;

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