c# using lambda to check if an object is of a certain dynamic type (passed via a parameter)

Question

I have a method that checks if a certain document is of a certain type and chooses to do something about it :

 private void OpenOrActivateDocument(Type FormType)
 {    var doc = dmMain.View.Documents.
          Where(x => x.Form is FormType).
          Select(x=>x).First();

          // do something about the found (or not found) doc
 }

this is a sample method that calls the above method:

private void button1_click(Object sender, EventArgs e)
{
        OpenOrActivateDocument(typeof(BudgetExtractionWindow));
}

however, I get an error here : "Where(x => x.Form is FormType)". If I were to change this to a specific type (that is not passed via the parameters), then i would not have a problem.

Answer 1

You should do it this way:

 private void OpenOrActivateDocument(Type FormType)
 {    var doc = dmMain.View.Documents.
          Where(x => x.Form.GetType() == FormType)
          .FirstOrDefault();

      if (doc != null){
          // do something about the found doc
      } else {
          //not found, do some other things
      }    
 }

The FormType is actually an object instance named FormType with class type Type . It does not represent any class name like what you normally use in class instance declaration: ClassType instance = new ClassType() .

If you want to check if your x.Form is of that type, you should use object's method GetType .

Also, you could remove the Select clause as it will be redundant.

FirstOrDefault is to make it return null when not found instead of throwing exception.