如何实现类的字符串名称与类本身的一致性？

Question

I have a comboBox at my Form. When i'm pressing it, list of the names of the classes popped up. And when i'm choosing some name of the class there, i want to create object of that class and then work with it. All my classes have a common parent, so i used this code to get all my sub classes:

var subclassTypes = Assembly
                    .GetAssembly(typeof(ParentClass))
                    .GetTypes()
                    .Where(t => t.IsSubclassOf(typeof(ParentClass)));

So after that i just added this to ComboBox , and its's work okay, it's showing all the classes i need in string. But how can i make an accordance between string name of the class and class itself? How can i store that accordance and how can i make it?

Answer 1

You already have all the Type s of your classes. Creating a new instance of one of them is then just something like (assuming comboboxSelection as the selected class name):

var classType = subclassTypes.First(t => t.Name == comboBoxSelection);
var classInstance = Activator.CreateInstance(classType);

Note that in the example classInstance is of type object . You can easily cast it to the common type though:

var classInstance = (ParentClass)Activator.CreateInstance(classType);

Note that for Activator.CreateInstance to work, the classes need to have a constructor without parameters.

Answer 2

You could store the types directly in the combobox and use the SelectedItem property to retrieve them in the SelectedIndexChanged event:

List<Type> subclassTypes = Assembly
        .GetAssembly(typeof(ParentClass))
        .GetTypes()
        .Where(t => t.IsSubclassOf(typeof(ParentClass))).ToList();


comboBoxTypes.DataSource = subclassTypes;
comboBoxTypes.DisplayMember = "Name";

Using the Activator.CreateInstance method you can create an object of that type.

private void ComboBoxTypes_SelectedIndexChanged(object sender, EventArgs e)
{
    Type itemType = comboBoxTypes.SelectedItem as Type;

    ParentClass item = (ParentClass)Activator.CreateInstance(itemType);
}

Disclaimer: this solution is for a parameterless constructor!