Selecting multiple columns with linq query and lambda expression

Question

I'm new to C# ASP.NET, and am working on my first application.

I'm trying to create a linq statment that return an arrary.

I have a table of products. I want to be able to select name, id, and price, for each product where the status == 1.

I am struggling with crating a way to do this. I have only been able to return individual items/columns. I have been stuck on this wayyy to long.

This is what I have so far:

try
{
  using (UserDataDataContext db = new UserDataDataContext())
  {
    return db.mrobProducts.Select(x => x.Name).OrderBy(x => x).ToArray();
  }
}

If you look in the screen shot below, you can see I have 2 errors, Select = Type object can not be refered from it's usage ToArray = cant resolve symbol to array

Answer 1

Not sure what you table structure is like but see below.

public NamePriceModel[] AllProducts()
{
    try
    {
        using (UserDataDataContext db = new UserDataDataContext())
        {
            return db.mrobProducts
                .Where(x => x.Status == 1)
                .Select(x => new NamePriceModel { 
                    Name = x.Name, 
                    Id = x.Id, 
                    Price = x.Price
                })
                .OrderBy(x => x.Id)
                .ToArray();
         }
     }
     catch
     {
         return null;
     }
 }

This would return an array of type anonymous with the members you require.

Update:

Create a new class.

public class NamePriceModel 
{
    public string Name {get; set;}
    public decimal? Price {get; set;}
    public int Id {get; set;}
}

I've modified the query above to return this as well and you should change your method from returning string[] to returning NamePriceModel[] .

Answer 2

You can use:

public YourClass[] AllProducts()
{
    try
    {
        using (UserDataDataContext db = new UserDataDataContext())
        {
            return db.mrobProducts.Where(x => x.Status == 1)
                           .OrderBy(x => x.ID)
                           .Select(x => new YourClass { ID = x.ID, Name = x.Name, Price = x.Price})
                           .ToArray();
        }
    }
    catch
    {
        return null;
    }
}

And here is YourClass implementation:

public class YourClass
{
  public string Name {get; set;}
  public int ID {get; set;}
  public int Price {get; set;}
}

And your AllProducts method's return type must be YourClass[] .

Answer 3

using LINQ and Lamba, i wanted to return two field values and assign it to single entity object field;

as Name = Fname + " " + LName;

See my below code which is working as expected; hope this is useful;

Myentity objMyEntity = new Myentity
{
id = obj.Id,
Name = contxt.Vendors.Where(v => v.PQS_ID == obj.Id).Select(v=> new { contact = v.Fname + " " + v.LName}).Single().contact
}

no need to declare the 'contact'

Answer 4

        Object AccountObject = _dbContext.Accounts
                                   .Join(_dbContext.Users, acc => acc.AccountId, usr => usr.AccountId, (acc, usr) => new { acc, usr })
                                   .Where(x => x.usr.EmailAddress == key1)
                                   .Where(x => x.usr.Hash == key2)
                                   .Select(x => new { AccountId = x.acc.AccountId, Name = x.acc.Name })
                                   .SingleOrDefault();