Calculator

Calculator simple implementation using C# code, four operations only (+,-,/,*) , the showAnswer function is called to print the operation results , the process is done as (FirstParameter Operation SecondParameter) . For numbers value you will notice that we defined button actions button1_Click,button2_Click,... button11_Click to take the number's values from the button text.
csharp code

using System; 
using System.Collections.Generic; 
using System.ComponentModel; 
using System.Data; 
using System.Drawing; 
using System.Linq; 
using System.Text; 
using System.Windows.Forms; 

namespace calculator 
{ 
public partial class Form1 : Form 
{ 
public Form1() 
{ 
InitializeComponent(); 
} 
private double FirstParameter; 

private double SecondParameter; 

private string cal; 

private bool inputstatus = true; 
private void button1_Click(object sender, EventArgs e) 
{ 
if (inputstatus) 
{ 
textBox1.Text += button1.Text; 
} 
else 
{ 
textBox1.Text = button1.Text; 
inputstatus = true; 
} 
} 

private void button2_Click(object sender, EventArgs e) 
{ 
if (inputstatus) 
{ 
textBox1.Text += button2.Text; 
} 
else 
{ 
textBox1.Text = button2.Text; 
inputstatus = true; 
} 
} 

private void button3_Click(object sender, EventArgs e) 
{ 
if (inputstatus) 
{ 
textBox1.Text += button3.Text; 
} 
else 
{ 
textBox1.Text = button3.Text; 
inputstatus = true; 
} 
} 

private void button4_Click(object sender, EventArgs e) 
{ 
if (inputstatus) 
{ 
textBox1.Text += button4.Text; 
} 
else 
{ 
textBox1.Text = button4.Text; 
inputstatus = true; 
} 
} 

private void button5_Click(object sender, EventArgs e) 
{ 
if (inputstatus) 
{ 
textBox1.Text += button5.Text; 
} 
else 
{ 
textBox1.Text = button5.Text; 
inputstatus = true; 
} 
} 

private void button6_Click(object sender, EventArgs e) 
{ 
if (inputstatus) 
{ 
textBox1.Text += button6.Text; 
} 
else 
{ 
textBox1.Text = button6.Text; 
inputstatus = true; 
} 
} 

private void button7_Click(object sender, EventArgs e) 
{ 
if (inputstatus) 
{ 
textBox1.Text += button7.Text; 
} 
else 
{ 
textBox1.Text = button7.Text; 
inputstatus = true; 
} 
} 

private void button8_Click(object sender, EventArgs e) 
{ 
if (inputstatus) 
{ 
textBox1.Text += button8.Text; 
} 
else 
{ 
textBox1.Text = button8.Text; 
inputstatus = true; 
} 
} 

private void button9_Click(object sender, EventArgs e) 
{ 
if (inputstatus) 
{ 
textBox1.Text += button9.Text; 
} 
else 
{ 
textBox1.Text = button9.Text; 
inputstatus = true; 
} 
} 

private void button10_Click(object sender, EventArgs e) 
{ 
if (inputstatus) 
{ 
textBox1.Text += button10.Text; 
} 
else 
{ 
textBox1.Text = button10.Text; 
inputstatus = true; 
} 
} 

private void button11_Click(object sender, EventArgs e) 
{ 
if (inputstatus) 
{ 
textBox1.Text += button11.Text; 
} 
else 
{ 
textBox1.Text = button11.Text; 
inputstatus = true; 
} 
} 

private void AddButton_Click(object sender, EventArgs e) 
{ 
if (textBox1.Text.Length != 0) 
{ 

FirstParameter = System.Double.Parse(textBox1.Text); 

showAnswer(); 

cal = "+"; 

} 
} 

private void SubButton_Click(object sender, EventArgs e) 
{ 
if (textBox1.Text.Length != 0) 
{ 

FirstParameter = System.Double.Parse(textBox1.Text); 

showAnswer(); 

cal = "-"; 

} 
} 

private void MutliButton_Click(object sender, EventArgs e) 
{ 
if (textBox1.Text.Length != 0) 
{ 

FirstParameter = System.Double.Parse(textBox1.Text); 

showAnswer(); 

cal = "*"; 

} 
} 

private void DivideButton_Click(object sender, EventArgs e) 
{ 
if (textBox1.Text.Length != 0) 
{ 

FirstParameter = System.Double.Parse(textBox1.Text); 

showAnswer(); 

cal = "/"; 

} 
} 

private void ClearField_Click(object sender, EventArgs e) 
{ 
showAnswer(); 

cal = string.Empty; 

} 

private void ClearAll_Click(object sender, EventArgs e) 
{ 
textBox1.Text = string.Empty; 

FirstParameter = 0; 

SecondParameter = 0; 

cal = string.Empty; 
} 
// Here we shoud results based on the selected operation
private void showAnswer() 
{ 

SecondParameter = System.Double.Parse(textBox1.Text); 

switch (cal) 
{ 

case "+": 

FirstParameter = FirstParameter + SecondParameter; 

break; 

case "-": 

FirstParameter = FirstParameter - SecondParameter; 

break; 

case "*": 

FirstParameter = FirstParameter * SecondParameter; 

break; 

case "/": 

FirstParameter = FirstParameter / SecondParameter; 

break; 

} 

textBox1.Text = FirstParameter.ToString(); 

inputstatus = false; 

} 
} 
}

updated.