سلام 
این کدی هستش که من نوشتم امیدوارم به دردت بخوره
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 ولی این درست کار میکنه
 public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        int total;
        int total1;
        bool button10_click=false;
        bool button12_click=false;
        bool button11_click = false;
        bool button13_click = false;
        private void button1_Click(object sender, EventArgs e)
        {
            textBox1.Text =textBox1.Text+button1.Text ;
        }
        private void button2_Click(object sender, EventArgs e)
        {
            textBox1.Text = textBox1.Text+button2.Text;
        }
        private void button3_Click(object sender, EventArgs e)
        {
            textBox1.Text = textBox1.Text+button3.Text;
        }
        private void button4_Click(object sender, EventArgs e)
        {
            textBox1.Text = textBox1.Text+button4.Text;
        }
        private void button5_Click(object sender, EventArgs e)
        {
            textBox1.Text = textBox1.Text+button5.Text;
        }
        private void button6_Click(object sender, EventArgs e)
        {
            textBox1.Text = textBox1.Text+button6.Text;
        }
        private void button7_Click(object sender, EventArgs e)
        {
            textBox1.Text = textBox1.Text+button7.Text;
        }
        private void button8_Click(object sender, EventArgs e)
        {
            textBox1.Text = textBox1.Text+button8.Text;
        }
        private void button9_Click(object sender, EventArgs e)
        {
            textBox1.Text = textBox1.Text+button9.Text;
        }
        private void button15_Click(object sender, EventArgs e)
        {
            textBox1.Text = textBox1.Text + button15.Text;
        }
        private void button16_Click(object sender, EventArgs e)
        {
            textBox1.Clear();
        }
        private void button10_Click(object sender, EventArgs e)
        {
            if (button12_click == true)
            {
                total1 = total - Convert.ToInt32(textBox1.Text);
                textBox1.Text= total1.ToString();
                total = 0;
            }
            if (button10_click == true)
            {
                total1 = total + Convert.ToInt32(textBox1.Text);
                textBox1.Text = total1.ToString();
                total = 0;
            }
            if (button11_click == true)
            {
                total1 = total * Convert.ToInt32(textBox1.Text);
                textBox1.Text = total1.ToString();
                total = 0;
            }
            if (button13_click == true)
            {
                total1 = total / Convert.ToInt32(textBox1.Text);
                textBox1.Text = total1.ToString();
                total = 0;
            }
            total = total + Convert.ToInt32(textBox1.Text);
            textBox1.Clear();
            button12_click = false;
            button10_click= true;
            button11_click = false;
            button13_click= false;
        }
        private void button14_Click(object sender, EventArgs e)
        {
            if (button10_click==true)
            {
                total1 = total + Convert.ToInt32(textBox1.Text);
               
            }
            
                if (button12_click==true)
                {
                    total1 = total - Convert.ToInt32(textBox1.Text);
            
                
                   }
                if (button11_click == true)
                {
                    total1 = total * Convert.ToInt32(textBox1.Text);
           
                }
                if (button13_click == true)
                {
                    total1 = total / Convert.ToInt32(textBox1.Text);
             
                }
                textBox1.Text = total1.ToString();
                total = 0;
                button12_click = false;
                button10_click = false;
                button11_click = false;
                button13_click = false;
        }
        private void button12_Click(object sender, EventArgs e)
        {
            if (button10_click == true)
            {
                total1 = total + Convert.ToInt32(textBox1.Text);
                textBox1.Text = total1.ToString();
                total = 0;
            }
            if (button11_click == true)
            {
                total1 = total * Convert.ToInt32(textBox1.Text);
                textBox1.Text = total1.ToString();
                total = 0;
            }
            if (button12_click == true)
            {
                total1 = total - Convert.ToInt32(textBox1.Text);
                textBox1.Text = total1.ToString();
                total = 0;
            }
            if (button13_click == true)
            {
                total1 = total / Convert.ToInt32(textBox1.Text);
                textBox1.Text = total1.ToString();
                total = 0;
            }
           total = total+Convert.ToInt32(textBox1.Text);
            textBox1.Clear();
            button12_click = true;
            button10_click = false;
            button11_click = false;
           button13_click= false;
        }
        private void button11_Click(object sender, EventArgs e)
        {
            if (button10_click == true)
            {
                total1 = total + Convert.ToInt32(textBox1.Text);
                textBox1.Text = total1.ToString();
                total = 0;
            }
            if (button11_click == true)
            {
                total1 = total * Convert.ToInt32(textBox1.Text);
                textBox1.Text = total1.ToString();
                total = 0;
            }
            if (button12_click == true)
            {
                total1 = total - Convert.ToInt32(textBox1.Text);
                textBox1.Text = total1.ToString();
                total = 0;
            }
            if (button13_click == true)
            {
                total1 = total / Convert.ToInt32(textBox1.Text);
                textBox1.Text = total1.ToString();
                total = 0;
            }
            total = total + Convert.ToInt32(textBox1.Text);
            textBox1.Clear();
            button12_click = false;
            button10_click = false;
            button11_click = true;
            button13_click = false;
        }
        private void button13_Click(object sender, EventArgs e)
        {
            if (button11_click == true)
            {
                total1 = total * Convert.ToInt32(textBox1.Text);
                textBox1.Text = total1.ToString();
                total = 0;
            }
            if(button13_click==true)
            {
                total1 = total / Convert.ToInt32(textBox1.Text);
                textBox1.Text = total1.ToString();
                total = 0;
            }
           if(button12_click==true)
            {
                total1 = total - Convert.ToInt32(textBox1.Text);
                textBox1.Text = total1.ToString();
                total = 0;
            }
            if(button11_click=true)
            {
                total1 = total + Convert.ToInt32(textBox1.Text);
                textBox1.Text = total1.ToString();
                total = 0;
            }
            total = total + Convert.ToInt32(textBox1.Text);
            textBox1.Clear();
            button12_click = false;
            button10_click = false;
            button11_click = false;
            button13_click= true;
        }
      
       
  
       
     
    }
}