CODEWITHSUNDEEP
c#asp.net
Samantha J T Star
Samantha J T Star

Reputation: 32778

How can I check if a value exists in a list using C#

I have the following code that gives me a list of id and names from the new ASP.NET MVC5 Identity:

        var identityStore = new IdentityStore();
        var users =
          (
              from user in identityStore.DbContext.Set<User>()
              select new
              {
                  id = user.Id,
                  name = user.UserName
              }
          );

How could I modify this so that it allows me to check if a UserName exists?

Here's the user class:

public class User : IUser
{
    public User();
    public User(string userName);

    [Key]
    public string Id { get; set; }
    public virtual ICollection<UserLogin> Logins { get; set; }
    public virtual UserManagement Management { get; set; }
    public virtual ICollection<UserRole> Roles { get; set; }
    public string UserName { get; set; }
}

Upvotes: 0

Views: 1089

Answers (2)

MichaC
MichaC

Reputation: 13380

You can query the username with a where statement if this is what you want, e.g.

var users = from user in identityStore.DbContext.Set<User>()
            where user.UserName != null && !user.UserName.Equals(string.Empty)
            select ...

anyways, it is a possible duplicate of this answer LINQ syntax where string value is not null or empty

string.IsNullOrEmpty does work only in some cases, so be careful!

Or if you just look for a specific user name, simply query for it

var users = from user in identityStore.DbContext.Set<User>()
            where user.UserName.Equals("whatever")
            select ...

Upvotes: 1

Fka
Fka

Reputation: 6234

if(identityStore.DbContext.Set<User>().Any(u => UserName == "yourUserName"))
{
    // user exists
}
else
{
    // user does not exist
}

Does it fit for your requirements? Your question is bit unclear.

Upvotes: 1

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