Dynamic string in linq c#

Question

I have installed System.Linq.Dynamic dll and then tried to add string as the parameter of WHERE clause in Linq. But I am still getting error that the string parameter is supported by WHERE clause.

Code:

_dbContext.TmRecords.Where("city=london");

Error:

Severity Code Description Project File Line Error CS1503 Argument 2: cannot convert from 'string' to 'System.Linq.Expressions.Expression>' Extranet.Domain

Here the city parameter dynamically changes to some other parameter. So, I need to use dynamic queries in linq.

You need to create a predicate, such as: `_dbContext.TmRecords.Where(record => record.city = "london");` — Markiian Benovskyi, Oct 20 '16 at 09:53
Possible duplicate of [Dynamic WHERE clause in LINQ](http://stackoverflow.com/questions/848415/dynamic-where-clause-in-linq) — santosh singh, Oct 20 '16 at 09:54
@Mark it's about [dynamic Linq](https://weblogs.asp.net/scottgu/dynamic-linq-part-1-using-the-linq-dynamic-query-library), not regular Linq — Kilazur, Oct 20 '16 at 09:54
My first guess in such cases would be that you forgot the correct `using` — Kilazur, Oct 20 '16 at 09:55
Do you have `using System.Linq.Dynamic;` at the top of your file? Without that, the only method that the compiler can find is the one expecting an expression and not a string. — DavidG, Oct 20 '16 at 09:57

score 7 · Accepted Answer · answered Oct 20 '16 at 09:59

7

You should add using System.Linq.Dynamic; to your file.

Also rewrite the query like this:

_dbContext.TmRecords.Where("city = @0", "london");

answered Oct 20 '16 at 09:59

Hamid Pourjam

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using the `@0` is necessary or just good practice? Thanks, this helped me aswell :) – Roy123 Oct 20 '16 at 10:03
The same thing how can i use it in lamda expression? – Dinesh Oct 20 '16 at 10:22
3

It is not necessary. You can use `"City == \"london\""` instead but using parameterized one is more readable IMHO. @Roy_Dorsthorst – Hamid Pourjam Oct 20 '16 at 10:31
If you have another question then ask it in new question. @dineshsns – Hamid Pourjam Oct 20 '16 at 10:32

Dynamic string in linq c#

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