'string' does not contain a definition for 'Contains'

Question

I have a statement like so:

var vals =
    from StandAloneUserPayment saup in _Session.Query<StandAloneUserPayment>()
        .Fetch(x => x.RecurringPayments)
    where
        saup.User.UserId == userId
        && searchString.Contains(saup.FriendlyName, StringComparer.InvariantCultureIgnoreCase)
    select
        saup;

This seems to be exactly what I'm supposed to do, but I get the whole line with the Contains method underlined with the following message:

string does not contain a definition for Contains and the best extension method overload System.Linq.ParallelEnumerable.Contains<TSource>(System.Linq.ParallelQuery<TSource>, TSource, System.Collections.Generic.IEqualityComparer<TSource>) has some invalid arguments

What am I doing wrong?

Ry- · Accepted Answer · 2016-03-15T00:45:54.703

17

Try IndexOf:

searchString.IndexOf(saup.FriendlyName,
                     StringComparison.InvariantCultureIgnoreCase) != -1

The reason it doesn't work is because the Contains extension method that accepts an IEqualityComparer<TSource> is operating on a String, which implements IEnumerable<char>, not IEnumerable<string>, so a string and an IEqualityComparer<string> can't be passed to it.

edited Mar 15 '16 at 00:45

answered Sep 10 '12 at 00:06

Ry-

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My intellisense would argue with you. It tells me I have three overloads. – Jeremy Holovacs Sep 10 '12 at 00:07
1

@JeremyHolovacs: And one of them takes a `StringComparer`? (Sorry, I can't try it right now, but MSDN is usually right...) – Ry- Sep 10 '12 at 00:08
as the error message implies, it takes an `IEqualityComparer`, which StringComparer implements. – Jeremy Holovacs Sep 10 '12 at 00:09
@JeremyHolovacs - are you sure you aren't using some kind of third party extension that supplies additional methods? – Erik Funkenbusch Sep 10 '12 at 00:09
1

@JeremyHolovacs extenstion methods? – Lukasz Madon Sep 10 '12 at 00:09
I think this is part of Linq. – Jeremy Holovacs Sep 10 '12 at 00:10
@JeremyHolovacs: Right... that's odd. Well, try `IndexOf` anyway. – Ry- Sep 10 '12 at 00:11
My intellisense said this: `(extention) bool IEnumerable.Contains(char value, IEqualityComparer comparer)` – CC Inc Sep 10 '12 at 00:13
@minitech Changing it to `IndexOf` gets me "The best overloaded method match for 'string.IndexOf(string, System.StringComparison)' has some invalid arguments"... I am scratching my head on this. – Jeremy Holovacs Sep 10 '12 at 00:14
Hah never mind I'm an idiot; `IndexOf` works if I change the `StringComparer` to `StringComparison`... `Contains` still doesn't work though. Well, it's good enough for me, thanks. – Jeremy Holovacs Sep 10 '12 at 00:16
@JeremyHolovacs: Is `saup.UserPayment` actually a `string`? – Ry- Sep 10 '12 at 00:16
2

@JeremyHolovacs: Oh yeah, and I just realized the reason `Contains` doesn't work; `String.Contains` is a special case because a `string` is an `IEnumerable`, not an `IEnumerable`. – Ry- Sep 10 '12 at 00:17
@minitech Can you expand your answer to explain? It might be useful for the next person scratching their head. I am marking this as the answer; thanks. – Jeremy Holovacs Sep 10 '12 at 00:19
@JeremyHolovacs: Sure, sorry. – Ry- Sep 10 '12 at 00:26
Then what the hell is this sirs? http://msdn.microsoft.com/en-us/library/dy85x1sa.aspx – Paul-Sebastian Manole Apr 12 '13 at 19:14
1

@Paul-SebastianManole: Documentation for a method called `Contains` on `String` that takes one argument, the second of which, it follows, is not an `IEqualityComparer`. – Ry- Apr 12 '13 at 22:45

score 3 · Answer 2 · answered Sep 10 '12 at 00:19

3

Even if there is a Contains(source, item, comparer) method, you can't* use that with NHibernate, as comparers are code, not expression trees that NH can translate.

*: that is, unless you write a LINQ provider extension that special-cases generation for your comparer, but that's not the case.

answered Sep 10 '12 at 00:19

Diego Mijelshon

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Odd that the intellisense lead me right into the problem. The IndexOf worked for what I needed, but it seems like that should work. – Jeremy Holovacs Sep 10 '12 at 00:21

score 2 · Answer 3 · answered Sep 10 '12 at 00:21

The .Contains you are using comes from LINQ - it sees the String as an IEnumerable<char>, so it wants an IEqualityComparer<char>. The StringComparer comparers implement IEqualityComparer<String>.

If minitech's IndexOf method works, I think that will be the easiest way.

score -3 · Answer 4 · answered Mar 13 '16 at 01:29

-3

Add following namespace to your class,

using System.Linq;

Hope it helps.

answered Mar 13 '16 at 01:29

Jogi

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'string' does not contain a definition for 'Contains'

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