فرم 1
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Data.SqlClient;
using System.Windows.Forms;
using System.IO;
namespace Accounter
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}

private void glassButton7_Click(object sender, EventArgs e)
{
lsitem.Visible = true;
lsuser.Visible = false;
}

private void btncustomer_Click(object sender, EventArgs e)
{

Form2 customer = new Form2();
if (Application.OpenForms["Form2"] == null)
{

customer.Show();
}
else
{
Application.OpenForms["Form2"].WindowState = FormWindowState.Normal;
Application.OpenForms["Form2"].Activate();

}

}

private void Form1_Load(object sender, EventArgs e)
{
user.Focus();
}

private void Form1_FormClosing(object sender, FormClosingEventArgs e)
{

}

private void Form1_FormClosed(object sender, FormClosedEventArgs e)
{
if (MessageBox.Show("آيا شما مي خواهيد از برنامه خارج شوید ؟", " خروج از برنامه", MessageBoxButtons.YesNo, MessageBoxIcon.Information, MessageBoxDefaultButton.Button1) == DialogResult.Yes)
Application.Exit();
}

private void glassButton2_Click(object sender, EventArgs e)
{

}
}
}

فرم 2-------------------------------------------------
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 Accounter
{
public partial class Form2 : Form
{
public Form2()
{
InitializeComponent();
}

private void Form2_Load(object sender, EventArgs e)
{
ra_code.Checked = true;
//disable();

}
public void disable()
{
//txt_adress.Enabled=false;
// txt_code.Enabled=false;
// txt_id.Enabled=false;
// txt_mobile.Enabled=false;
// txt_money.Enabled=false;
// txt_name.Enabled=false;
// txt_phone.Enabled=false;
//data.Enabled=false;

}
private void btn_search_Click(object sender, EventArgs e)
{
if (search.Visible) search.Visible = false;
else
{
search.Visible = true;
numericUpDown1.Focus();
}
}

private void ra_code_CheckedChanged(object sender, EventArgs e)
{
if (ra_code.Checked)
{
txt_searchname.Enabled = false;
txt_searchname.BackColor = Color.WhiteSmoke;
numericUpDown1.Enabled = true;
numericUpDown1.BackColor = Color.White;
data_search.Enabled = false;
data_search.BackColor = Color.WhiteSmoke;
}
}


private void ra_customer_CheckedChanged(object sender, EventArgs e)
{
if (ra_customer.Checked)
{
txt_searchname.Enabled = true;
txt_searchname.BackColor = Color.White;
txt_searchname.Focus();
numericUpDown1.Enabled = false;
numericUpDown1.BackColor = Color.WhiteSmoke;
data_search.Enabled = false;
data_search.BackColor = Color.WhiteSmoke;
}
}

private void ra_data_CheckedChanged(object sender, EventArgs e)
{
if (ra_data.Checked)
{
txt_searchname.Enabled = false;
txt_searchname.BackColor = Color.WhiteSmoke;
numericUpDown1.Enabled = false;
numericUpDown1.BackColor = Color.WhiteSmoke;
data_search.Enabled = true;
data_search.BackColor = Color.White;
}
}

private void btn_new_Click(object sender, EventArgs e)
{
// enable();
}

private void Form2_FormClosed(object sender, FormClosedEventArgs e)
{

}
}
}