How to copy value from class X to class Y with the same property name in c#?

The lists make it tricky… my earlier reply (below) only applies to like-for-like properties (not the lists). I suspect you might just have to write and maintain code:

    Student foo = new Student {
        Id = 1,
        Name = "a",
        Courses = {
            new Course { Key = 2},
            new Course { Key = 3},
        }
    };
    StudentDTO dto = new StudentDTO {
        Id = foo.Id,
        Name = foo.Name,
    };
    foreach (var course in foo.Courses) {
        dto.Courses.Add(new CourseDTO {
            Key = course.Key
        });
    }

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edit; only applies to shallow copies – not lists

Reflection is an option, but slow. In 3.5 you can build this into a compiled bit of code with Expression. Jon Skeet has a pre-rolled sample of this in MiscUtil – just use as:

Student source = ...
StudentDTO item = PropertyCopy<StudentDTO>.CopyFrom(student);

Because this uses a compiled Expression it will vastly out-perform reflection.

If you don’t have 3.5, then use reflection or ComponentModel. If you use ComponentModel, you can at least use HyperDescriptor to get it nearly as quick as Expression

Student source = ...
StudentDTO item = new StudentDTO();
PropertyDescriptorCollection
     sourceProps = TypeDescriptor.GetProperties(student),
     destProps = TypeDescriptor.GetProperties(item),
foreach(PropertyDescriptor prop in sourceProps) {
    PropertyDescriptor destProp = destProps[prop.Name];
    if(destProp != null) destProp.SetValue(item, prop.GetValue(student));
}