expected class delegate enum interface or struct at void

Question

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Windows.Forms;

using System.IO;

namespace WindowsFormsApplication1

{

public partial class Form1 : Form

{

public Form1()

{

InitializeComponent();

}

public void Form1_Load(object sender, EventArgs e)

{

}

public void button1_Click(object sender, EventArgs e)

{

TextWriter tw = new StreamWriter(@"D:\Registration.txt", true);

string name, address, country, pincode, email;

name = textBox1.Text;

address = textBox2.Text;

pincode = textBox3.Text;

email = textBox4.Text;

Decription=textBox5.Text;

textBox5.Multiline = true;

string gender;

if((radioButton1.Checked == true))

{

gender = "Male";

}

else

{

gender = "Female";

}

country = comboBox1.Text;

if(comboBox1.Items.Count==0)

{

comboBox1.Items.Insert(0,"India");

comboBox1.Items.Insert(1,"America");

comboBox1.Items.Insert(2,"SriLanka");

comboBox1.Items.Insert(3,"Dubai");

comboBox1.Text="-select-";

}

else

{

if(string.IsNullOrEmpty("combobox1.selectedvalue"))

{

comboBox1selectedvalue=Convert.ToInt32(comboBox1.SelectedValue);

}

}

if(comboBox1selectedvalue!=null)

{

comboBox1.SelectedValue=comboBox1selectedvalue.Tostring();

}

}

private void checkBox1_CheckedChanged(object sender, EventArgs e)

{

string language;

if(checkBox1.Checked==true)

{

language="c#";

}

if(checkBox2.Checked==true)

{

language=language+"vb";

}

if(language.Length>0)

{

MessageBox.Show(language+"selected");

}

else

{

MessageBox.Show("not selected");

}

checkBox1.ThreeState=true;

}

}

}

tw.WriteLine("-----------------------");

tw.WriteLine("Details");

tw.WriteLine("name :" + name);

tw.WriteLine("address :" + address);

tw.WriteLine("country :" + comboBox1.SelectedItem.ToString());

tw.WriteLine("pincode :" + pincode);

tw.WriteLine("Email :" + email);

tw.WriteLine("Gender :" + gender);

tw.WriteLine("Language :" + language);

tw.WriteLine("Decription :" + decription);

tw.WriteLine("------------------------");

tw.Close();

Clear();

public void Clear()

{

textBox1.Text = "";

textBox2.Text = "";

comboBox1.Text = "";

textBox3.Text = "";

textBox4.Text = "";

radioButton1.Text = "";

radioButton2.Text = "";

checkBox1.Text = " ";

checkBox2.Text = " ";

textBox5.Text = "";

}

iam getting error: 

1.expected class delegate enum interface or struct at void

2. a namespace cannot directly contain members such as fields or methods how to slove these errors