Click-through in C# Form

Click-through in C# Form - c#

I've created a semi-transparent form. I'd like for people to be able to click on the form area, and for form not handle the click. I'd like whatever is underneath the form to receive the click event instead.

You can do this with SetWindowLong:
int initialStyle = GetWindowLong(this.Handle, -20);
SetWindowLong(this.Handle, -20, initialStyle | 0x80000 | 0x20);
There are a few magic numbers in here:
-20 – GWL_EXSTYLE
Retrieves the extended window styles.
0x80000 – WS_EX_LAYERED
Creates a layered window.
0x20 – WS_EX_TRANSPARENT
Specifies that a window created with this style should not be painted until siblings beneath the window (that were created by the same thread) have been painted. The window appears transparent because the bits of underlying sibling windows have already been painted.
There are numerous articles all over the web on how to do this, such as this one.

The SetWindowLong in #Joey's answer can only make the form semi-transparent after showing the form on screen. If you call SetWindowLong in Form1_Load, the form will be opaque upon creation, and then quickly being changed to semi-transparent. This causes the users to see the non-semi-transparent form for a short moment upon launching the program. To prevent this, you can override CreateParams instead :
public partial class Form1 : Form
{
protected override CreateParams CreateParams
{
get
{
const int WS_EX_LAYERED = 0x80000;
const int WS_EX_TRANSPARENT = 0x20;
CreateParams cp = base.CreateParams;
cp.ExStyle |= WS_EX_LAYERED;
cp.ExStyle |= WS_EX_TRANSPARENT;
return cp;
}
}
}
The code above makes the form semi-transparent before showing the form on screen.
The solution above is similar to this post, which makes the form top-most instead.

Related

form slow loading when go to another form in C# [duplicate]

In my application i am constantly moving from one control to another. I have created no. of user controls, but during navigation my controls gets flicker. it takes 1 or 2 sec to update. I tried to set this
SetStyle(ControlStyles.OptimizedDoubleBuffer, true);
or
SetStyle(ControlStyles.UserPaint, true);
SetStyle(ControlStyles.AllPaintingInWmPaint, true);
SetStyle(ControlStyles.DoubleBuffer, true);
but it didn't help... Each control has same background image with different controls.
So what is the solution for it..
Thanks.

It is not the kind of flicker that double-buffering can solve. Nor BeginUpdate or SuspendLayout. You've got too many controls, the BackgroundImage can make it a lot worse.
It starts when the UserControl paints itself. It draws the BackgroundImage, leaving holes where the child control windows go. Each child control then gets a message to paint itself, they'll fill in the hole with their window content. When you have a lot of controls, those holes are visible to the user for a while. They are normally white, contrasting badly with the BackgroundImage when it is dark. Or they can be black if the form has its Opacity or TransparencyKey property set, contrasting badly with just about anything.
This is a pretty fundamental limitation of Windows Forms, it is stuck with the way Windows renders windows. Fixed by WPF btw, it doesn't use windows for child controls. What you'd want is double-buffering the entire form, including the child controls. That's possible, check my code in this thread for the solution. It has side-effects though, and doesn't actually increase painting speed. The code is simple, paste this in your form (not the user control):
protected override CreateParams CreateParams {
get {
CreateParams cp = base.CreateParams;
cp.ExStyle |= 0x02000000; // Turn on WS_EX_COMPOSITED
return cp;
}
}
There are many things you can do to improve painting speed, to the point that the flicker isn't noticeable anymore. Start by tackling the BackgroundImage. They can be really expensive when the source image is large and needs to be shrunk to fit the control. Change the BackgroundImageLayout property to "Tile". If that gives a noticeable speed-up, go back to your painting program and resize the image to be a better match with the typical control size. Or write code in the UC's OnResize() method to create a properly sized copy of the image so that it doesn't have to be resized every time the control repaints. Use the Format32bppPArgb pixel format for that copy, it renders about 10 times faster than any other pixel format.
Next thing you can do is prevent the holes from being so noticeable and contrasting badly with the image. You can turn off the WS_CLIPCHILDREN style flag for the UC, the flag that prevents the UC from painting in the area where the child controls go. Paste this code in the UserControl's code:
protected override CreateParams CreateParams {
get {
var parms = base.CreateParams;
parms.Style &= ~0x02000000; // Turn off WS_CLIPCHILDREN
return parms;
}
}
The child controls will now paint themselves on top of the background image. You might still see them painting themselves one by one, but the ugly intermediate white or black hole won't be visible.
Last but not least, reducing the number of child controls is always a good approach to solve slow painting problems. Override the UC's OnPaint() event and draw what is now shown in a child. Particular Label and PictureBox are very wasteful. Convenient for point and click but their light-weight alternative (drawing a string or an image) takes only a single line of code in your OnPaint() method.

This is a real issue, and the answer Hans Passant gave is great for saving the flicker. However, there are side effects as he mentioned, and they can be ugly (UI ugly). As stated, "You can turn off the WS_CLIPCHILDREN style flag for the UC", but that only turns it off for a UC. The components on the main form still have issues.
Example, a panel scroll bar doesn't paint, because it is technically in the child area. However the child component doesn't draw the scroll bar, so it doesn't get painted until mouse over (or another event triggers it).
Also, animated icons (changing icons in a wait loop) doesn't work. Removing icons on a tabPage.ImageKey doesn't resize/repaint the other tabPages appropriately.
So I was looking for a way to turn off the WS_CLIPCHILDREN on initial painting so my Form will load nicely painted, or better yet only turn it on while resizing my form with a lot of components.
The trick is to get the application to call CreateParams with the desired WS_EX_COMPOSITED/WS_CLIPCHILDREN style. I found a hack here (https://web.archive.org/web/20161026205944/http://www.angryhacker.com/blog/archive/2010/07/21/how-to-get-rid-of-flicker-on-windows-forms-applications.aspx) and it works great. Thanks AngryHacker!
I put the TurnOnFormLevelDoubleBuffering() call in the form ResizeBegin event and TurnOffFormLevelDoubleBuffering() call in the form ResizeEnd event (or just leave it WS_CLIPCHILDREN after it is initially painted properly.)
int originalExStyle = -1;
bool enableFormLevelDoubleBuffering = true;
protected override CreateParams CreateParams
{
get
{
if (originalExStyle == -1)
originalExStyle = base.CreateParams.ExStyle;
CreateParams cp = base.CreateParams;
if (enableFormLevelDoubleBuffering)
cp.ExStyle |= 0x02000000; // WS_EX_COMPOSITED
else
cp.ExStyle = originalExStyle;
return cp;
}
}
public void TurnOffFormLevelDoubleBuffering()
{
enableFormLevelDoubleBuffering = false;
this.MaximizeBox = true;
}

If you are doing any custom painting in the control (i.e. overriding OnPaint) you can try the double buffering yourself.
Image image;
protected override OnPaint(...) {
if (image == null || needRepaint) {
image = new Bitmap(Width, Height);
using (Graphics g = Graphics.FromImage(image)) {
// do any painting in image instead of control
}
needRepaint = false;
}
e.Graphics.DrawImage(image, 0, 0);
}
And invalidate your control with a property NeedRepaint
Otherwise the above answer with SuspendLayout and ResumeLayout is probably what you want.

Put the code bellow in your constructor or OnLoad event and if you're using some sort of custom user control that having sub controls, you'll need to make sure that these custom controls are also double buffered (even though in MS documentation they say it's set to true by default).
If you're making a custom control, you might want to add this flag into your ctor:
SetStyle(ControlStyles.OptimizedDoubleBuffer, true);
Optionally you can use this code in your Form/Control:
foreach (Control control in Controls)
{
typeof(Control).InvokeMember("DoubleBuffered",
BindingFlags.SetProperty | BindingFlags.Instance | BindingFlags.NonPublic,
null, control, new object[] { true });
}
We iterating through all the controls in the form/control and accessing their DoubleBuffered property and then we change it to true in order to make each control on the form double buffered. The reason we do reflection here, is because imagine you have a control that has child controls that are not accessible, that way, even if they're private controls, we'll still change their property to true.
More information about double buffering technique can be found here.
There is another property I usually override to sort this problem:
protected override CreateParams CreateParams
{
get
{
CreateParams parms = base.CreateParams;
parms.ExStyle |= 0x00000020; // WS_EX_COMPOSITED
return parms;
}
}
WS_EX_COMPOSITED - Paints all descendants of a window in bottom-to-top painting order using double-buffering.
You can find more of these style flags here.
Hope that helps!

Try BeginUpdate/EndUpdate OR SuspendLayout/ResumeLayout methods.
See following
How to fix nested winform control flicker issues
Flickering during updates to Controls in WinForms (e.g. DataGridView)

Just to add to the answer Hans gave:
(TLDR version: Transparency is heavier than you think, use only solid colors everywhere)
If WS_EX_COMPOSITED, DoubleBuffered and WS_CLIPCHILDREN did not solve your flicker (for me WS_CLIPCHILDREN made it even worse), try this: go through ALL your controls and all your code, and wherever you have Any transparency or semi-transparency for BackColor, ForeColor, or any other color, just remove it, use only solid colors. In most of the cases where you think you just have to use transparency, you don't. Re-design your code and controls, and use solid colors.
I had terrible, terrible flickering and the program was running sluggish. Once I removed transparency it sped up significantly, and there is 0 flicker.
EDIT: To add further, I just discovered that WS_EX_COMPOSITED doesn't have to be window-wide, it could be applied just to specific controls! This saved me a lot of trouble. Just make a custom control inherited from whatever control you need, and paste the already posted override for WS_EX_COMPOSITED. This way you get low-level double-buffer on this control only, avoiding the nasty side-effects in the rest of the application!

On the main form or user control where background image resides set the BackgroundImageLayout property to Center or Stretch. You will notice a big difference when the user control is rendering.

I tried to add this as a comment but I don't have enough points. This is the only thing that's ever helped my flickering problems so many thanks to Hans for his post. For anyone that's using c++ builder like myself here's the translation
Add the CreateParams declaration to your application's main form .h file e.g.
class TYourMainFrom : public TForm
{
protected:
virtual void __fastcall CreateParams(TCreateParams &Params);
}
and add this to your .cpp file
void __fastcall TYourMainForm::CreateParams(TCreateParams &Params)
{
Params.ExStyle |= 0x02000000; // Turn on WS_EX_COMPOSITED
TForm::CreateParams(Params);
}

I know this question is very old, but want to give my experience on it.
I had a lot of problems with Tabcontrol flickering in a form with overrided OnPaint and/or OnPaintBackGround in Windows 8 using .NET 4.0.
The only think that worked has been NOT USE the Graphics.DrawImage method in OnPaint overrides, in other words, when draw was done directly to the Graphics provided by the PaintEventArgs, even painting all the rectangle, the flickering dissapeared. But if call the DrawImage method, even drawing a clipped Bitmap, (created for double buffering) the flicker appears.
Hope it helps!

I combined this flicker fix and this font fix, then I had to add a bit of my own code to start a timer on paint to Invalidate the TabControl when it goes offscreen and back, etc..
All three make this:
using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;
public class TabControlEx:TabControl
{
[DllImport("user32.dll")]
private static extern IntPtr SendMessage(IntPtr hWnd, int Msg, IntPtr wParam, IntPtr lParam);
private const int WM_PAINT = 0x0f;
private const int WM_SETFONT = 0x30;
private const int WM_FONTCHANGE = 0x1d;
private System.Drawing.Bitmap buffer;
private Timer timer = new Timer();
public TabControlEx()
{
timer.Interval = 1;
timer.Tick += timer_Tick;
this.SetStyle(ControlStyles.UserPaint | ControlStyles.DoubleBuffer | ControlStyles.AllPaintingInWmPaint, true);
}
void timer_Tick(object sender, EventArgs e)
{
this.Invalidate();
this.Update();
timer.Stop();
}
protected override void WndProc(ref Message m)
{
if (m.Msg == WM_PAINT) timer.Start();
base.WndProc(ref m);
}
protected override void OnPaint(PaintEventArgs pevent)
{
this.SetStyle(ControlStyles.UserPaint, false);
base.OnPaint(pevent);
System.Drawing.Rectangle o = pevent.ClipRectangle;
System.Drawing.Graphics.FromImage(buffer).Clear(System.Drawing.SystemColors.Control);
if (o.Width > 0 && o.Height > 0)
DrawToBitmap(buffer, new System.Drawing.Rectangle(0, 0, Width, o.Height));
pevent.Graphics.DrawImageUnscaled(buffer, 0, 0);
this.SetStyle(ControlStyles.UserPaint, true);
}
protected override void OnResize(EventArgs e)
{
base.OnResize(e);
buffer = new System.Drawing.Bitmap(Width, Height);
}
protected override void OnCreateControl()
{
base.OnCreateControl();
this.OnFontChanged(EventArgs.Empty);
}
protected override void OnFontChanged(EventArgs e)
{
base.OnFontChanged(e);
IntPtr hFont = this.Font.ToHfont();
SendMessage(this.Handle, WM_SETFONT, hFont, (IntPtr)(-1));
SendMessage(this.Handle, WM_FONTCHANGE, IntPtr.Zero, IntPtr.Zero);
this.UpdateStyles();
}
}
I'm not the creator but from what I understand the bitmap does all the bug bypassing.
This was the only thing that definitively solved TabControl (with Icons) flicker for me.
difference result video: vanilla tabcontrol vs tabcontrolex
http://gfycat.com/FineGlitteringDeermouse
ps. you will need to set HotTrack = true, because this fixes that bug too

Did you try Control.DoubleBuffered Property?
Gets or sets a value indicating whether this control should redraw its surface using a secondary buffer to reduce or prevent flicker.
Also this and this might help.

There is no need of any Double buffering and all that stuff guys...
A Simple solution...
If you are using MDI Interface, just paste the code below in the main form. It will remove all flickering from the pages. However some pages which require more time for loading will showup in 1 or 2 secs. But this is better than showing a flickering page in which each item comes one by one.
This is the only best solution for whole application. See the code to put in the main form:
protected override CreateParams CreateParams {
get {
CreateParams cp = base.CreateParams;
cp.ExStyle |= 0x02000000; // Turn on WS_EX_COMPOSITED
return cp;
}
}

Prebuffering Form when minimized [duplicate]

In my application i am constantly moving from one control to another. I have created no. of user controls, but during navigation my controls gets flicker. it takes 1 or 2 sec to update. I tried to set this
SetStyle(ControlStyles.OptimizedDoubleBuffer, true);
or
SetStyle(ControlStyles.UserPaint, true);
SetStyle(ControlStyles.AllPaintingInWmPaint, true);
SetStyle(ControlStyles.DoubleBuffer, true);
but it didn't help... Each control has same background image with different controls.
So what is the solution for it..
Thanks.

This is a real issue, and the answer Hans Passant gave is great for saving the flicker. However, there are side effects as he mentioned, and they can be ugly (UI ugly). As stated, "You can turn off the WS_CLIPCHILDREN style flag for the UC", but that only turns it off for a UC. The components on the main form still have issues.
Example, a panel scroll bar doesn't paint, because it is technically in the child area. However the child component doesn't draw the scroll bar, so it doesn't get painted until mouse over (or another event triggers it).
Also, animated icons (changing icons in a wait loop) doesn't work. Removing icons on a tabPage.ImageKey doesn't resize/repaint the other tabPages appropriately.
So I was looking for a way to turn off the WS_CLIPCHILDREN on initial painting so my Form will load nicely painted, or better yet only turn it on while resizing my form with a lot of components.
The trick is to get the application to call CreateParams with the desired WS_EX_COMPOSITED/WS_CLIPCHILDREN style. I found a hack here (https://web.archive.org/web/20161026205944/http://www.angryhacker.com/blog/archive/2010/07/21/how-to-get-rid-of-flicker-on-windows-forms-applications.aspx) and it works great. Thanks AngryHacker!
I put the TurnOnFormLevelDoubleBuffering() call in the form ResizeBegin event and TurnOffFormLevelDoubleBuffering() call in the form ResizeEnd event (or just leave it WS_CLIPCHILDREN after it is initially painted properly.)
int originalExStyle = -1;
bool enableFormLevelDoubleBuffering = true;
protected override CreateParams CreateParams
{
get
{
if (originalExStyle == -1)
originalExStyle = base.CreateParams.ExStyle;
CreateParams cp = base.CreateParams;
if (enableFormLevelDoubleBuffering)
cp.ExStyle |= 0x02000000; // WS_EX_COMPOSITED
else
cp.ExStyle = originalExStyle;
return cp;
}
}
public void TurnOffFormLevelDoubleBuffering()
{
enableFormLevelDoubleBuffering = false;
this.MaximizeBox = true;
}

If you are doing any custom painting in the control (i.e. overriding OnPaint) you can try the double buffering yourself.
Image image;
protected override OnPaint(...) {
if (image == null || needRepaint) {
image = new Bitmap(Width, Height);
using (Graphics g = Graphics.FromImage(image)) {
// do any painting in image instead of control
}
needRepaint = false;
}
e.Graphics.DrawImage(image, 0, 0);
}
And invalidate your control with a property NeedRepaint
Otherwise the above answer with SuspendLayout and ResumeLayout is probably what you want.

Put the code bellow in your constructor or OnLoad event and if you're using some sort of custom user control that having sub controls, you'll need to make sure that these custom controls are also double buffered (even though in MS documentation they say it's set to true by default).
If you're making a custom control, you might want to add this flag into your ctor:
SetStyle(ControlStyles.OptimizedDoubleBuffer, true);
Optionally you can use this code in your Form/Control:
foreach (Control control in Controls)
{
typeof(Control).InvokeMember("DoubleBuffered",
BindingFlags.SetProperty | BindingFlags.Instance | BindingFlags.NonPublic,
null, control, new object[] { true });
}
We iterating through all the controls in the form/control and accessing their DoubleBuffered property and then we change it to true in order to make each control on the form double buffered. The reason we do reflection here, is because imagine you have a control that has child controls that are not accessible, that way, even if they're private controls, we'll still change their property to true.
More information about double buffering technique can be found here.
There is another property I usually override to sort this problem:
protected override CreateParams CreateParams
{
get
{
CreateParams parms = base.CreateParams;
parms.ExStyle |= 0x00000020; // WS_EX_COMPOSITED
return parms;
}
}
WS_EX_COMPOSITED - Paints all descendants of a window in bottom-to-top painting order using double-buffering.
You can find more of these style flags here.
Hope that helps!

Try BeginUpdate/EndUpdate OR SuspendLayout/ResumeLayout methods.
See following
How to fix nested winform control flicker issues
Flickering during updates to Controls in WinForms (e.g. DataGridView)

Just to add to the answer Hans gave:
(TLDR version: Transparency is heavier than you think, use only solid colors everywhere)
If WS_EX_COMPOSITED, DoubleBuffered and WS_CLIPCHILDREN did not solve your flicker (for me WS_CLIPCHILDREN made it even worse), try this: go through ALL your controls and all your code, and wherever you have Any transparency or semi-transparency for BackColor, ForeColor, or any other color, just remove it, use only solid colors. In most of the cases where you think you just have to use transparency, you don't. Re-design your code and controls, and use solid colors.
I had terrible, terrible flickering and the program was running sluggish. Once I removed transparency it sped up significantly, and there is 0 flicker.
EDIT: To add further, I just discovered that WS_EX_COMPOSITED doesn't have to be window-wide, it could be applied just to specific controls! This saved me a lot of trouble. Just make a custom control inherited from whatever control you need, and paste the already posted override for WS_EX_COMPOSITED. This way you get low-level double-buffer on this control only, avoiding the nasty side-effects in the rest of the application!

On the main form or user control where background image resides set the BackgroundImageLayout property to Center or Stretch. You will notice a big difference when the user control is rendering.

I tried to add this as a comment but I don't have enough points. This is the only thing that's ever helped my flickering problems so many thanks to Hans for his post. For anyone that's using c++ builder like myself here's the translation
Add the CreateParams declaration to your application's main form .h file e.g.
class TYourMainFrom : public TForm
{
protected:
virtual void __fastcall CreateParams(TCreateParams &Params);
}
and add this to your .cpp file
void __fastcall TYourMainForm::CreateParams(TCreateParams &Params)
{
Params.ExStyle |= 0x02000000; // Turn on WS_EX_COMPOSITED
TForm::CreateParams(Params);
}

I know this question is very old, but want to give my experience on it.
I had a lot of problems with Tabcontrol flickering in a form with overrided OnPaint and/or OnPaintBackGround in Windows 8 using .NET 4.0.
The only think that worked has been NOT USE the Graphics.DrawImage method in OnPaint overrides, in other words, when draw was done directly to the Graphics provided by the PaintEventArgs, even painting all the rectangle, the flickering dissapeared. But if call the DrawImage method, even drawing a clipped Bitmap, (created for double buffering) the flicker appears.
Hope it helps!

I combined this flicker fix and this font fix, then I had to add a bit of my own code to start a timer on paint to Invalidate the TabControl when it goes offscreen and back, etc..
All three make this:
using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;
public class TabControlEx:TabControl
{
[DllImport("user32.dll")]
private static extern IntPtr SendMessage(IntPtr hWnd, int Msg, IntPtr wParam, IntPtr lParam);
private const int WM_PAINT = 0x0f;
private const int WM_SETFONT = 0x30;
private const int WM_FONTCHANGE = 0x1d;
private System.Drawing.Bitmap buffer;
private Timer timer = new Timer();
public TabControlEx()
{
timer.Interval = 1;
timer.Tick += timer_Tick;
this.SetStyle(ControlStyles.UserPaint | ControlStyles.DoubleBuffer | ControlStyles.AllPaintingInWmPaint, true);
}
void timer_Tick(object sender, EventArgs e)
{
this.Invalidate();
this.Update();
timer.Stop();
}
protected override void WndProc(ref Message m)
{
if (m.Msg == WM_PAINT) timer.Start();
base.WndProc(ref m);
}
protected override void OnPaint(PaintEventArgs pevent)
{
this.SetStyle(ControlStyles.UserPaint, false);
base.OnPaint(pevent);
System.Drawing.Rectangle o = pevent.ClipRectangle;
System.Drawing.Graphics.FromImage(buffer).Clear(System.Drawing.SystemColors.Control);
if (o.Width > 0 && o.Height > 0)
DrawToBitmap(buffer, new System.Drawing.Rectangle(0, 0, Width, o.Height));
pevent.Graphics.DrawImageUnscaled(buffer, 0, 0);
this.SetStyle(ControlStyles.UserPaint, true);
}
protected override void OnResize(EventArgs e)
{
base.OnResize(e);
buffer = new System.Drawing.Bitmap(Width, Height);
}
protected override void OnCreateControl()
{
base.OnCreateControl();
this.OnFontChanged(EventArgs.Empty);
}
protected override void OnFontChanged(EventArgs e)
{
base.OnFontChanged(e);
IntPtr hFont = this.Font.ToHfont();
SendMessage(this.Handle, WM_SETFONT, hFont, (IntPtr)(-1));
SendMessage(this.Handle, WM_FONTCHANGE, IntPtr.Zero, IntPtr.Zero);
this.UpdateStyles();
}
}
I'm not the creator but from what I understand the bitmap does all the bug bypassing.
This was the only thing that definitively solved TabControl (with Icons) flicker for me.
difference result video: vanilla tabcontrol vs tabcontrolex
http://gfycat.com/FineGlitteringDeermouse
ps. you will need to set HotTrack = true, because this fixes that bug too

Did you try Control.DoubleBuffered Property?
Gets or sets a value indicating whether this control should redraw its surface using a secondary buffer to reduce or prevent flicker.
Also this and this might help.

There is no need of any Double buffering and all that stuff guys...
A Simple solution...
If you are using MDI Interface, just paste the code below in the main form. It will remove all flickering from the pages. However some pages which require more time for loading will showup in 1 or 2 secs. But this is better than showing a flickering page in which each item comes one by one.
This is the only best solution for whole application. See the code to put in the main form:
protected override CreateParams CreateParams {
get {
CreateParams cp = base.CreateParams;
cp.ExStyle |= 0x02000000; // Turn on WS_EX_COMPOSITED
return cp;
}
}

Black flashbacks when resize wpf element host

I have a WPF UserControl that displayed in a Winform as Element Host.
When I change the screen size quickly or resize it I see a black flashbacks in the background until the UserControl comes to the appropriate size.
I read about it in several places.
All the places I read them talk it happens only in the UserControl Load and bring solutions accordingly.
One question I've seen talking about it happening on Resize. But the solution offered there is as well to Load.
Black background on resizing elementhost
I tried on Resize of the screen to perform the following: UserControl.CreateGraphics (); , it does not leaves black lines like the above answer said.
I guess it's because I used it in Resize and not on Load.
Besides, I could not find anything.
If anyone encountered this and found a solution I would love to answer.

We usually face flickering issues while developing windows application with forms having many controls on it. A very neat way to get rid of this flickering is double buffering the whole form and its child controls. However, this would not speed up the control painting but it will hold the screen for a while and just show the updated screen instead of flickering. To implement this we need to enable the WS_EX_COMPOSITED flag. Just add the following code to your form's code.
C#:
protected override CreateParams CreateParams
{
get
{
CreateParams cp = base.CreateParams;
cp.ExStyle |= 0x02000000;
// Turn on WS_EX_COMPOSITED
return cp;
}
}
VB .net:
Protected Overrides ReadOnly Property CreateParams() As CreateParams
Get
Dim cp As CreateParams = MyBase.CreateParams
cp.ExStyle = cp.ExStyle Or &H2000000
Return cp
End Get
End Property

What helped me in the end it following lines of code (in Winform):
protected override void OnResize(EventArgs e)
{
this.SuspendLayout();
base.OnResize(e);
this.ResumeLayout();
}

Controls not being drawn at the same time

I have a form which I'm bringing up using ShowDialog which contains a couple of text boxes, labels and a button. The problem I'm having is that the text boxes are being drawn before the form itself and the other controls are drawn.
I am overriding the OnPaint method I'm not sure if this could be causing the problem:
protected override void OnPaint(PaintEventArgs e)
{
ControlPaint.DrawBorder(e.Graphics, e.ClipRectangle, Color.Black, ButtonBorderStyle.Solid);
base.OnPaint(e);
}
It's only a slight delay but it's visible and annoying. Thank you.
The form is double buffered by the way.
EDIT: I have pinpointed the issue to be the fact that the form does not have a FormBorderStyle. With the FormBorderStyle set to Sizable, this issue does not occur. However please note that having FormBorderStyle.None as my border style is necessary, so I have not found a solution yet.

Try adding this to the dialog box form:
protected override CreateParams CreateParams
{
get
{
// Activate double buffering at the form level. All child controls will be double buffered as well.
CreateParams cp = base.CreateParams;
cp.ExStyle |= 0x02000000; // WS_EX_COMPOSITED
return cp;
}
}

Flicker free TextBox

I have a simple Winforms multiline TextBox on my Form. Whenever I resize or move the TextBox its content starts to flicker madly. That looks very disgusting and might even cause epileptic seizure for some users ;-)
Is there a way to manipulate the redrawing process of the TextBox to get rid of the flickering?

I've found a working solution on the MSDN forums written by Hans Passant. The following code can be added to the form and will work for all child controls, too:
protected override CreateParams CreateParams {
get {
const int WS_EX_COMPOSITED = 0x02000000;
CreateParams cp = base.CreateParams;
cp.ExStyle |= WS_EX_COMPOSITED;
return cp;
}
}

afaik you can't control the resize mode of single controls on a form...
in my opinion you have 2 options:
find out why the flickering occurs - graphics driver issues?
set the ResizeRedraw property of the form to false
http://msdn.microsoft.com/en-us/library/system.windows.forms.control.resizeredraw.aspx

Develop Reference

C# (C-Sharp) is a programming language developed by Microsoft that runs on the .NET Framework.