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c#entity-frameworklinqlambda
Danki
Danki

Reputation: 95

Entity Framework with LINQ query

What is difference between change / change2?

using (var context = new NORTHWNDEntities())
{
    var change = context.Regions.Where(r => r.RegionDescription == "East").ToList();

    var change2 = (from r in context.Regions where r.RegionDescription == "East" select new {r.RegionID, r.RegionDescription }).ToList();

    foreach (var p in change2)
    {
        p.RegionDescription = "West";
    }
    context.SaveChanges();
}

When I trying to make update on change2 in foreach loop i got error:

Property or indexer '......' cannot be assigned to -- it is read only

It works on previous version with lambda. How Can i change it to work?

Upvotes: 1

Views: 60

Answers (2)

Johnathan Barclay
Johnathan Barclay

Reputation: 20373

change2 returns an anonymous type which is immutable. To amend the value, you need to write:

var change2 = (from r in context.Regions where r.RegionDescription == "East" select r).ToList();

Which is equivalent to change1.

Upvotes: 1

TyCobb
TyCobb

Reputation: 9089

 var change2 = (from r in context.Regions 
                where r.RegionDescription == "East" 
                select new {r.RegionID, r.RegionDescription }).ToList();

You are returning an anonymous type. Anonymous type properties are read-only. If you want to change the value, you need to return an actual type that you have defined.

You can either new something else like new Region or just return r

var change2 = (from r in context.Regions 
                where r.RegionDescription == "East" 
                select r).ToList(); 


 var change2 = (from r in context.Regions 
                where r.RegionDescription == "East" 
                select new Region {.RegionID = r.RegionID, 
                                   .RegionDescription = r.RegionDescription }).ToList();

Upvotes: 2

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