C# - Pulling Out Different Columns From Tables Using LINQ

I have two tables:

Entity
ID (PK), int
Name
Descrip
Users
ID (PK)
EntityID, int (this is not connected to Entity table)

Now I am using LINQ to pull the records which has a Entity.ID = something. Which will show me couple of records in my GridView. Here is my LINQ statement:

protected void Page_Load(object sender, EventArgs e)
{
string getEntity = Request.QueryString["EntityID"];
int getIntEntity = Int32.Parse(getEntity);
OISEntityTestingDataContext db = new OISEntityTestingDataContext();
//OISLinqtoSQLDataContext db = new OISLinqtoSQLDataContext();
var tr =
from r in db.Users
join s in db.Entities on r.UserID equals s.ID
where s.ID == getIntEntity
select new
{
//To Show Items in GridView!
};
GridView1.DataSource = tr;
GridView1.DataBind();
}

Now here I am getting an error mesg on 'join' The type of one of the expressions in the join clause is incorrect. Type inference failed in the call to 'Join What does that mean?