Linq Query that returns IQueryable

I have a method called

     public static IQueryable GetUsers()

uses Linq query.

{SELECT [t0].[ApplicationUserId], ([t0].[LastName] + @p0) + [t0开发者_Go百科].[FirstName] AS [UserName], [t1].[SecurityRoleName], [t2].[UserStatus]
    FROM [dbo].[ApplicationUsers] AS [t0]
    INNER JOIN [dbo].[SecurityRoles] AS [t1] ON [t0].[SecurityRoleId] = [t1].[SecurityRoleID]
    INNER JOIN [dbo].[UserStatusLookups] AS [t2] ON [t0].[UserStatusId] = [t2].[UserStatusLookupID]
    ORDER BY [t0].[LastName]
}

that returns all the users. I cannot the change this method or class.

I need a user belonging to a specific security role. From just IQueryable would I be able to get a specific user. so that [t1].[SecurityRoleID] is replaced with 15.

You can't use Where because it's only defined on IQueryable<T>, the strongly-typed version. You need to cast your IQueryable from GetUsers() to an appropriate IQueryable<T>:

var users = GetUsers().Cast<ModelType>();

ModelType should be whatever type the model objects from GetUsers are; it should have SecurityRoleID, ApplicationUserId, or whatever properties you need.

Then you can use the LINQ extension methods:

var user = users.Where(u => u.SecurityRoleID == 15);

or maybe:

var user = users.FirstOrDefault(u => u.SecurityRoleID == 15);

This should do it:

var Role15Users = GetUsers().Where(t => t.SecurityRoldID == 15);

You can use a where on your full list

var users = MyClass.GetUsers();
var userInRole = users.Where(u=>u.SecurityRoleId == 15);

Do you have

using System.Linq

in your includes?

Where<TSource> Method (IQueryable<TSource>, Expression<Func<TSource, Boolean>>)

is an extension method to the IQueryable type found in the System.Linq namespace.

It is also quite possible that there's no SecurityRoleId property in the class, rather an object relation. In this case you would have to write something like

var roleUsers = dataSource.GetUsers().Where(
    u => u.SecurityRole.Id == 15
    );

It would return all users with role #15.
However you sure must know that magic number are bad.

If you want to find a single user with role called, for instance, Admin, make sure SecurityRole is correctly mapped (depends on your class structure which you haven't posted) and do something like

var admin = (from user in dataSource.GetUsers()
            where user.SecurityRole.Name == "Administrator"
            select user).Single(); // will throw exception if none or multiple are found


var admin = (from user in dataSource.GetUsers()
            where user.SecurityRole.Name == "Administrator"
            select user).SingleOrDefault(); // will return null if none, throw exception if multiple are found

You can also rewrite these queries in method call fashion:

var admin = dataSource.GetUsers()
    .Where(u => u.SecurityRole.Name == "Administrator")
    .Single(); // will throw exception if none or multiple are found

var admin = dataSource.GetUsers()
    .Where(u => u.SecurityRole.Name == "Administrator")
    .SingleOrDefault(); // will return null if none, throw exception if multiple are found