Cannot convert lambda expression to type 'string' because it is not a delegate type

Question

In my controller i am trying to use include with EF4 to select related entities, but the lambda expression is throwing the following error,

i have the related entity defined in the Entity class like

public class CustomerSite
{
    public int CustomerSiteId { get; set; }
    public int CustomerId { get; set; }
    public virtual Customer Customer { get; set; }
}

Then in my controller i have

 var sites = context.CustomerSites.Include(c => c.Customer);

 public ViewResult List()
 {
    var sites = context.CustomerSites.Include(c => c.Customer);
    return View(sites.ToList());
 }

Can anyone kindly point me in the right direction on what i'm doing wrong here?

lejlot · Accepted Answer · 2013-09-04 15:29:57Z

97

Well, the post is quite old, but just replying here to update it. Well, the Include() method with Entity Framework 4.1 has extension methods and it also accepts a lambda expression. So

context.CustomerSites.Include(c => c.Customer);

is perfectly valid, all you need to do is use this:

using System.Data.Entity;

edited Sep 4, 2013 at 15:29

lejlot

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answered Feb 24, 2012 at 9:55

amarnath chatterjee

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Comments

Will · Accepted Answer · 2013-05-24 08:49:29Z

13

Include is an extension method in the System.Data.Entity namespace, you need to add:

using System.Data.Entity;

Then you can use the lambda expression, instead of the string.

answered May 24, 2013 at 8:49

Will

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Comments

Darin Dimitrov · Accepted Answer · 2011-07-14 16:06:57Z

9

The Include method expects a string, not a lambda:

public ViewResult List()
{
    var sites = context.CustomerSites.Include("Customer");
    return View(sites.ToList());
}

Of course you could write a custom extension method which would work with lambda expressions and make your code independant of some magic strings and refactor friendlier.

But whatever you do PLEASE OH PLEASE don't pass EF autogenerated objects to your views. USE VIEW MODELS.

answered Jul 14, 2011 at 16:06

Darin Dimitrov

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5 Comments

Liam Over a year ago

thanks, but easier said than done, i cant find a solid example of how to use view models to return related data

Pomster Over a year ago

@Darin Dimitrov Could you please come look at a similar question i have posted. stackoverflow.com/q/16060884/1356321

Bolt Thunder Over a year ago

Could you please give a reference to the update below: stackoverflow.com/a/9428710/1268910

Fenton Over a year ago

Definitely check out the alternate answer for later versions of Entity Framework, as lambdas are allowed.

Pxtl Over a year ago

Above answer is out-of-date. Correct answer is below. ``` using System.Data.Entity; ```

SLaks · Accepted Answer · 2011-07-14 16:06:57Z

2

Include takes a string, not a lambda expression.
Change it to CustomerSites.Include("Customer")

answered Jul 14, 2011 at 16:06

SLaks

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Comments

Dan Is Fiddling By Firelight · Accepted Answer · 2019-06-14 20:11:10Z

1

If you are getting this error in Razor:

Ex:

@Html.RadioButtonFor(model => model.Security, "Fixed", new { @id = "securityFixed"})

C# doesn't know how to convert the string to valid bool or known type.

So change your string as below:

@Html.RadioButtonFor(model => model.Security, "True", new { @id = "securityFixed"})

or

@Html.RadioButtonFor(model => model.Security, "False", new { @id = "securityFixed"})

edited Jun 14, 2019 at 20:11

Dan Is Fiddling By Firelight

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answered Jan 20, 2014 at 1:57

Nalan Madheswaran

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