C# winforms cast childform as of it's own type

I have MDI project. I'm using Form activeForm = this.ActiveMdiChild;

However, Instead of Form I'm for something like

Forms.Lookup.Grade activeForm = (Forms.Lookup.Grade) this.ActiveMdiChild; Forms.Lookup.Product activeForm = (Forms.Lookup.Product) this.ActiveMdiChild; ...etc so if Forms.Lookup.Grade is active I want return activeForm as Forms.Lookup.Grade

How can I cast active form as of it's own type in generic way instead of using Switch this.ActiveMdiChild.Name ?

Thank You Mansi