Linq to sql in how to make join query

Here you can find examples for join in LinQ.

C# Join[^]

I think in your linq query the problem was caused by the difference of the type between the pd.id and od.No. The type of the two columns must be the same!

var query2 = (from pd in db.Student1s
              join od in db.Test_1s on pd.id equals od.No
              select new 
                {
                    od.Name,
                    pd.name
                }).ToList();

You need to check the following

1. that pd.id and od.No are the same type.
2. if either variable is nullable that you change the query to read from the Value property of the variables

for an example look here

The type of one of the expressions int he join clause is incorrect. Type inference failed in the call to 'join'[^]