C # programming----> Calculating circle Area Windows programs

What's worth saying is adding a carriage return event,

http://blog.csdn.net/nanwang314/article/details/6176604

private void Textbox1_keydown (object sender, System.Windows.Forms.KeyEventArgs e)     {           if (e.keycode== Keys.enter)           {                 MessageBox.Show ("You pressed the Enter key in TextBox1");           }     

This way you can add a carriage return event .....

usingSystem;usingSystem.Collections.Generic;usingSystem.ComponentModel;usingSystem.Data;usingSystem.Drawing;usingSystem.Linq;usingSystem.Text;usingSystem.Threading.Tasks;usingSystem.Windows.Forms;namespacecircleareaw{ Public Partial classForm1:form { PublicForm1 () {InitializeComponent (); }        Private voidButton1_Click (Objectsender, EventArgs e) {            DoubleR; R=Double.            Parse (Txtr.text); Mycircle acircle=Newmycircle (R); DoubleAarea =Acircle.circlearea (); Dblarea.text= Aarea.tostring ("f4"); }        Private voidTxtr_keydown (Objectsender, KeyEventArgs e) {            if(E.keycode = =keys.enter) {MessageBox.Show ("you pressed the Enter key in the TextBox1."); DoubleR; R=Double.                Parse (Txtr.text); Mycircle acircle=Newmycircle (R); DoubleAarea =Acircle.circlearea (); Dblarea.text= Aarea.tostring ("f4"); }        }    }}

Form1.cs

usingSystem;usingSystem.Collections.Generic;usingSystem.Linq;usingSystem.Text;usingSystem.Threading.Tasks;namespacecircleareaw{classmycircle {DoubleCircler;  PublicMycircle (DoubleDBLR) {Circler=Dblr; }         Public DoubleCirclearea () {DoubleDblarea = Math.PI * Circler *Circler; returnDblarea; }    }}

C # programming----> Calculating circle Area Windows programs