how to retrieve checked value of checkbox from sql server 2005 using C# on windows form

Try following code

    Dim query As String = "INSERT INTO TABLENAME (CheckBoxColumn) VALUES (@CheckBoxColumn)"
    Dim conn As New SqlClient.SqlConnection("Connection String")
    Dim cmd As New SqlClient.SqlCommand(query, conn)
    If CheckBox1.Checked = True Then
      cmd.Parameters.Add("@CheckBoxColumn", SqlDbType.Bit).Value = 1
    Else
      cmd.Parameters.Add("@CheckBoxColumn", SqlDbType.Bit).Value = 0
    End If

    conn.Open()
    cmd.ExecuteNonQuery()
    conn.Close()

You can get connection string from http://www.connectionstrings.com.