Question

Please consider the following code:

class Student
{
}

enum StudentType
{
}

static void foo(IDictionary<StudentType, IList<Student>> students)
{   
}

static void Main(string[] args)
{
    Dictionary<StudentType, List<Student>> studentDict = 
                     new Dictionary<StudentType, List<Student>>();

    foo(studentDict);

    ...
}

There is the error:

error CS1503: Argument ‘1’: cannot
convert from
‘System.Collections.Generic.Dictionary>’
to
‘System.Collections.Generic.IDictionary>’

Is there any way to call foo function?

Answer 1

You could use the Linq ToDictionary method to create a new dictionary where the value has the correct type:

static void Main(string[] args)
{
  Dictionary<StudentType, List<Student>> studentDict = new Dictionary<StudentType, List<Student>>();
  var dicTwo = studentDict.ToDictionary(item => item.Key, item => (IList<Student>)item.Value);
  foo(dicTwo);
}