[DllImport("Kernel32.dll")]
public static extern bool SetProcessWorkingSetSize(IntPtr hWnd, int minSize, int maxSize);
 
public void FlushMemory()
{
    GC.Collect();
    GC.WaitForPendingFinalizers();
 
    if (Environment.OSVersion.Platform == PlatformID.Win32NT)
        SetProcessWorkingSetSize(System.Diagnostics.Process.GetCurrentProcess().Handle, -1 -1);
 
/*Using System.Runtime.InteropService*/
}

/*Функция для получение TextBox из активной вкладке TabControl*/
private TextBox GetTBox()
{
    TextBox TBox = null;
    TabPage TPage = tabControl.SelectedTab;
 
    if (TPage != null)
        TBox = TPage.Controls[0] as TextBox;
 
    return TBox;
}
/*Загружаем*/
private void LoadFile()
{
    StreamReader Sr = new StreamReader("C:\\Text.txt", Encoding.Default);
 
    GetTBox().Text

private string GetNetworkStatus()
{
    Ping pingNet = new Ping();
    PingReply pingReply = pingNet.Send(@"yandex.ru");
    IPStatus ipStatus = pingReply.Status;
 
    if (ipStatus ==  IPStatus.Success)
        return "Интернет подключен";
    else
        return "Интернет не подключен";
 
/*Using System.Net*/
}

[DllImport("UxTheme.dll", ExactSpelling = true, CharSet = CharSet.Unicode)]
public static extern in SetWindowTheme(IntPtr hWnd, string supAppName, string subIdList);
 
 /*TreeView*/
SetWindowTheme(treeView.Handle, "Explorer", null);
 /*ListView*/
SetWindowTheme(listView.Handle, "Explorer", null);
 /*ListBox*/
SetWindowTheme(listBox.Handle, "Explorer", null);
 
/*Using System.Runtime.InteropService*/

private void LoadFile(string FileName, Encoding encText)
{
    StreamReader Sr = new StreamReader(FileName, encText);
    
    textBox.Text = Sr.ReadToEnd();
    Sr.Close();
}
private void SaveFile(string FileName, Encoding encText)
{
    StreamWriter Sw = new StreamWriter(FileName);
    
    Sw.WriteLine(textBox.Text, encText);
    Sw.Flush();
    Sw.Close();
}
/*Using System.IO*/