show/create form from variable

I am still learning C# so I am sorry if I do not use the correct terminology.

Here is what I am trying to do. I have the following code that I use to check to see if an instance of a form already exists, and if it does show it. Otherwise it creates the form and then shows it.

Code:

 private void btnAdd_Click(object sender, EventArgs e)
        {
            if (chbDetail.Checked == true)
            {
                bool exists = false;

                foreach (Form f in Application.OpenForms)
                {
                    if (object.ReferenceEquals(f.GetType(), typeof(Ingredient)))
                    {
                        exists = true;
                        break;
                    }
                }

                if (exists)
                {
                    Ingredient ingredient = (Ingredient)Application.OpenForms["Ingredient"];
                    ingredient.Show();
                }
                else
                {
                    Ingredient ingredient = new Ingredient();
                    ingredient.Show();
                }
            }
        }

The problem is that I need to do this with multiple forms in different parts of my program, so I wanted to create a class that I could just pass a variable into and have it open any form I wanted. I thought about using a switch but then I am still writing the code out multiple times. Any ideas would be appreciated.