.net - How to append text to the richTextBox from another class in C# Winform? -

i have created winform namedform1 richtextbox namedrichtextbox1. have created method called update work of displaying message in richtextbox1. when tried invoke class1 not working. whereas see message in messagebox whereas not in richtextbox1. here piece of code.

code: form1.cs

public partial class form1 : form     {         public form1()         {             initializecomponent();         }         public void update(string message)         {             richtextbox1.appendtext("mess: " + message);             messagebox.show(message);         }          private void form1_load(object sender, eventargs e)         {             class1 sample = new class1();                     }      } 

class1.cs

public class class1     {                 public class1()         {             form1 form = new form1();             form.update("sampe");         }             } 

try this:

class1.cs

 class class1     {         public class1()         {             form1._form1.update("sampe");         }      } 

form1.cs

 public partial class form1 : form     {         public form1()         {             initializecomponent();             _form1 = this;         }         public static  form1 _form1;         public void update(string message)         {             richtextbox1.appendtext("mess: " + message);             messagebox.show(message);         }          private void form1_load(object sender, eventargs e)         {             class1 sample = new class1();         }     }