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C# Windows Form Application Transparent button

I'm new to C#. I'd like to create an invisible button, but they are click-able in C# windows form application. Is there a way? I tried BackColor to Transparent, but that does not change the fact that it is transparent

Its simple try this.
Click the button that you want to make transparent.
Select FlatStyle from Properties and set it to popup
Now change the BackColor property to Transparent.
This will make the button transparent.
However if you want to make it transparent over a PictureBox this method wont work..
It works only on normal backgrounds and background images.
Hope it works....

buttonLink.FlatStyle = FlatStyle.Flat;
buttonLink.BackColor = Color.Transparent;
buttonLink.FlatAppearance.MouseDownBackColor = Color.Transparent;
buttonLink.FlatAppearance.MouseOverBackColor = Color.Transparent;

The answers given just make the background color of the control you want to make transparent the same as the background color of its parent. It's not true transparency and windows forms doesn't support true transparency.
Windows Forms controls do not support true transparency. The background of a
transparent Windows Forms control is painted by its parent.
https://learn.microsoft.com/en-us/dotnet/desktop/winforms/controls/how-to-give-your-control-a-transparent-background?view=netframeworkdesktop-4.8&redirectedfrom=MSDN

Reference:
Original article and code can be found at:
Displaying a ToolTip when the Mouse Hovers Over a Disabled Control
# CodeProject by tetsushmz
Code:
public class TransparentSheet : ContainerControl
{
public TransparentSheet()
{
// Disable painting the background.
this.SetStyle(ControlStyles.Opaque, true);
this.UpdateStyles();
// Make sure to set the AutoScaleMode property to None
// so that the location and size property don't automatically change
// when placed in a form that has different font than this.
this.AutoScaleMode = AutoScaleMode.None;
// Tab stop on a transparent sheet makes no sense.
this.TabStop = false;
}
private const short WS_EX_TRANSPARENT = 0x20;
protected override CreateParams CreateParams
{
[SecurityPermission(SecurityAction.LinkDemand, UnmanagedCode = true)]
get
{
CreateParams l_cp;
l_cp = base.CreateParams;
l_cp.ExStyle = (l_cp.ExStyle | WS_EX_TRANSPARENT);
return l_cp;
}
}
}
Explanation:
What you need to do is use the given control as an overlay on your disabled TextBox (that you mentioned in one of your comments). Sibscribe to the overlay control's Click event and you have yourself a click on a disabled control.
I strongly recommend against this approach and feel it is kind of a hack. You really should look for an alternative approach instead of having to use a disabled control with an overlay control on top of it.
Maybe a different UI or atleast wrap it up in a UserControl to isolate this messy logic.

Setting the background property of the button to transparent will still leave a border. If you want a completely transparent button, do one of 2 things:
Create a transparent panel and assign a method to the Click event
or preferably
Create a custom UserControl that is filled with only BackColor (set to transparent) and assign method to Click event.
public class Invisible_Button : UserControl
{
protected override void OnMouseMove(MouseEventArgs e)
{
base.OnMouseMove(e);
this.Cursor = Cursors.Hand;
}
protected override void OnPaint(PaintEventArgs e)
{
base.OnPaint(e);
e.Graphics.FillRectangle(new SolidBrush(this.BackColor), 0, 0, this.Width, this.Height);
}
}

Did you try button.Visible = false?
If all you want is to hide it, this will do the job.

Prevent Button from inheriting BackColor of Parent

When I have a parent control which has a BackColor other than SystemColors.Control, but I have buttons on that parent control that I want to be drawn in the system them. However, when I do not change the BackColor of the buttons, it's drawn in the color of the parent. When I change the BackColor of the button to SystemColors.Control, it isn't drawn in the Windows theme anymore.
The left version is with SystemColors.Control and the right is without changing the BackColor.
Blown up, it looks like this. Here you can see that the buttons have a solid background.
Any suggestions how I can fix this?
The effect in the image can be accomplished by creating a new .NET 2.0 WinForms project and changing the constructor of Form1 to the following:
public Form1()
{
InitializeComponent();
var textBox = new TextBox();
Controls.Add(textBox);
var button = new Button { Text = "L", Width = 23, Height = 18, Left = -1, Top = -1 };
textBox.Controls.Add(button);
// Disable the line below to get the default behavior
button.BackColor = SystemColors.Control;
}

I unforuantely only have access to Windows 7 at the moment so I can't test on XP etc. but are you calling Application.EnableVisualStyles in the Main entry point of your WinForms application?
On Windows 7 with Aero enabled the buttons do not assume the parent color if Application.EnableVisualStyles is called.
NB: You should set button.UseVisualStyleBackColor = true; and do not explicitly set the BackColor property of the button.

How to dock a windows form in C#?

I just would like to know if it is possible to dock a windows form on top of the user screen? I have been trying to do this by manually setting the position of my form to the coordinates I want. But using this method, however, allows the user to change the position of the form just by dragging it. I want to make the form docked to the upper portion of the screen since this window form will server as a menu for the project I am making.
Thanks a lot. :)

I would consider using the Control.Dock property along with one of the DockStyle enumeration values.
You might need to play with the Layout too, so that you may layout your form's controls differently depending on the DockStyle selected.
You will need, in my point of view, to consider the Control.Location property so that you get to know which DockStyle value to dock your form with.
EDIT #1
Your Windows Form has a Dock property as it inherits from Control.
Let's consider the following :
Each time your form comes closer to your right-side of the screen, for example, or of the MDI container, you want to dock right, right ? (Little word play here... =P) So, you have to subscribe to the Control.LocationChanged event.
private void myForm_LocationChanged(object sender, EventArgs e) {
if (this.Location.X > 900) then
this.Dock = DockStyle.Right;
else if (this.Location.X < 150) then
this.Dock = DockStyle.Left;
else if (this.Location.Y > 600) then
this.Dock = DockStyle.Bottom;
else if (this.Location.Y < 150) then
this.Dock = DockStyle.Top;
else
this.Dock = DockStyle.None;
}
Indeed, instead of constant values, you should use the current desktop resolution and calculate a ratio from it where you want your docking to occur.
***Disclaimer:****This code is provided as-is and has not been tested. This algorithm is hopefully enough to guide you through the docking process as you need it. Further assistance may be brought upon request.* =)
It seems the Form.DesktopLocation property is the righter tool for the job as for your main window, meaning your MDI container, for instance. As for the other windows, I would go along with something that looks like the code sample provided.
Does this help?
EDIT #2
If you want to prevent Form's overlapping, perhaps the Control.BringToFront() method could do it before or after your call to the Control.Show() method, depending on what works best for you.

So after some tweaks I finally was able to get this code working.
this.DesktopLocation = new Point((Screen.PrimaryScreen.Bounds.Width / 2 - 420), 0);
I placed that line below the InitializeComponent() and it docks my form to the center of the screen with whatever resolution values.

By setting the FormBorderStyle of your form to None, you take the drag handle away from the user so they cannot move it via the mouse.
Then you just need to place it where you want.
If you really want to take away the users options you can also set the ShowInTaskbar property to false

How do I make a form transparent while keeping the controls fully visible?

I would like to have a form in which the controls on the form are fully visible but the form itself is invisible. If I change the form's Opacity, this makes both the form and the controls on it semi-transparent, so this doesn't work.
I can't do this by setting the form's TransparencyKey, since I have a PictureBox on the form. If the image in the PictureBox happens to contain pixels that match the TransparencyKey, they appear as openings in the form, which I don't want.

TransparencyKey is the only way to get this. Pick the right color. Color.Fuchsia has a long tradition of being the color of choice, going back to the early days of Win32 development. Assault your eye with it to see its merits.

With the caveat that I've never used it, just ran across it once, thought "neat!" and moved on...
Look into System.Drawing.Drawing2D.GraphicsPath and setting the form's Region property. I added two buttons to the basic Windows forms application:
public Form1()
{
InitializeComponent();
Rectangle r1 = new Rectangle(button1.Location, button1.Size);
Rectangle r2 = new Rectangle(button2.Location, button2.Size);
GraphicsPath gp = new GraphicsPath();
gp.AddRectangle(r1);
gp.AddRectangle(r2);
this.Region = new Region(gp);
}
I've approximated the shape of the button with a rectangle; with this code, you can see the form background color at the buttons' corners. You'll need to work out the enclosing path for each of your controls and add them to the path individually. You'll need to take into account any offset introduced by the form title bar or border style.
Update: I did some investigation and have a couple of possible approaches for the problem:
Using the GraphicsPath method, set pictureBox.Visible to False if there is no image loaded.
When you load an image into the picture box, analyze the image to get a list of all the colors in it, then randomly generate one that isn't. Set the form's BackColor and TransparencyKey properties to match this new color, Hans Passant's answer.

Equivalent of Swing's pack in C#

I am developing a quick app in C#. One thing that I want to do is the equivalent of Swing's (java) pack(). This is a call that allows me to say to a form (Frame in Java), resize yourself to the size of the sum of the components within yourself.
I have searched and searched (the components change dynamically so I cannot simply hardcode the form to the right size) but I cannot find the equivalent method in C#.
Does anyone know what it is called?

You don't even need write code in order to 'pack' the form. In the forms designer, set the form's AutoSize property to true, and set the AutoSizeMode property to GrowAndShrink, repeat this for any controls on the form which may also change size.
And voila!
At runtime (only), the form will dynamically resize itself to accommodate all the controls. If you want it to keep a little distance from the controls so that the controls won't 'stick' to the edges, you can set the Padding property (I'd recommend at least a value of 12,12,12,12).

Also in xaml:
<Window SizeToContent="WidthAndHeight" />

Another solution, available only if the image is smaller than the screen:
Form frm = new Form();
PictureBox pbx = new PictureBox();
pbx.Image = Image.FromFile( _imagePath.Text );
pbx.Dock = DockStyle.Fill;
frm.Controls.Add( pbx );
frm.Size = pbx.Image.Size;
frm.Show();