Month: October 2022

I need to make inner join on 3 tables; LedgerTypes, LedgerControl and Ledger.

Method based query example

//method based query
            
// your starting point - table in the "from" statement
var list = LedgerTypes
  //the source table of the inner join
  .Join(LedgerControl,
     //primary key (first part of sql "join" statement)
     t => t.Id,
     //foreign key (the second part of the "on" clause)
     lc => lc.ControllerTypeId, 
  (t, lc) => new { t, lc })   //new join
  // third table in the join clause
  .Join(Ledger, 
    //third table foreign key
    tc => tc.lc.Id, 
    //second table primary key
    l => l.ControllerID, 
  (tc, l) => new { tc, l })
      .Select(result => new {          //selection
       LedgerTypeId = result.tc.t.Id,
       LedgerTypeName = result.tc.t.ControllerTypeName,
       LedgerControlId = result.tc.lc.Id,
       LedgerControlName = result.tc.lc.ControllerCodeFullName,
       LedgerId = result.tc.lc.Id,
       LedgerName = result.tc.lc.ControllerCodeFullName
       // other assignments
});

Linq based query example

 //linq based query
var list = from t in LedgerTypes
    join lc in LedgerControl on t.Id equals lc.ControllerTypeId
    join l in Ledger on lc.Id equals l.ControllerID
    select new
       {
             LedgerTypeId = t.Id,
             LedgerTypeName = t.ControllerTypeName,
             LedgerControlId = lc.Id,
             LedgerControlName = lc.ControllerCodeFullName,
             LedgerId = l.Id,
             LedgerName = l.LedgerCodeFullName
            // other assignments
       };

I prefer query syntax because it’s readable and maintainable.

Resources

For more info read here and here