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Accessibility in TextBox in Windows Form - Visual Studio

I'm new to visual studio and I'm developing an application for visually impaired. I'm testing my application with NVDA. The audio feedback I'm getting on moving focus to a TextBox using tab button is just "Edit-Blank". I want to change that to a custom text. How can I do that?

That has nothing to do with accessibility, actually. When developing for accessibility, please always keep in mind the following: a blind (deaf, ...) user must get the same info as all of your users, starting from yourself, unless you absolutely need to convey something that is inaccessible otherwise (a visual tooltip instead of a sound for deaf users, an alternative text description of an image for blind users, etc.).
Here NVDA tells you what you actually get: the edit box is blank, indeed. If you want to describe the box, you need a label, not something in the text box (let the user enter his/her text in it). So:
private Label myLabel;
// ...
this.myLabel = new Label();
// ...
this.myLabel.Text = "Your Name:";
and place that label to the left (or above) the edit box. You may also set AccessibleRole, if you want:
this.myLabel.AccessibleRole = AccessibleRole.StaticText;
I suggest to do this if your form is actually a dialog box.

You need to put a Label control into the form and update the TabIndex properties of the Label and TextBox, so that the Label's TabIndex value is one less than the TextBox's TabIndex value (e.g. label1.TabIndex == 1 and textBox1.TabIndex == 2).
Then, the Text of the Label will be read when entering the TextBox.

To make a TextBox more accessible by NVDA you can perform either of the following settings:
You can set AccessibleName
You can set AccessibleDescription
You can put a Label control near the TextBox having immediate TabIndex before the TextBox.
For Narrator you can perform either of the following settings:
You can set AccessibleName
You can set Cue Banner for the TextBox.
You can put a Label control near the TextBox having immediate TabIndex before the TextBox.

How make an area on win form scrollable?

Items like below have to be accommodated on a specific area on WinForm.
"Order 1 ------------ Time Left: 00:20:00"
"Order 2 ------------ Time Left: 01:30:20"
We should be able to perform the following action on the each order:
Each item will occupy not more than one line. As the area specified
for it on the win form is limited, as more items comes in, I want to
make the area scrollable.
According to the time left the background color of the line should also change.
There is a DONE button next to it. So, if the item is selected and DONE is pressed, the item is moved off the list.
My question is what C# Form control can be used for it. I was thinking of labels, but how to make the area scrollable if there are many of them. If not labels, what else is suggested?

As suggested in comments, you can use grid, but in case it does not suits your requirements, this is like something what you can do -
Create a custom user control which will have a label control for your order detail and a Done button. Something like this (sure you will design it better!). The label will be empty initially and you will pass then from outside, using a public property for example, while creating the control.
Define an Event on this control, and raise this event when the Done button is clicked. This is required for your main form to know that when to remove this user control.
Add a FlowLayoutPanel to your main form. This will be the container for your user controls. Make sure to set the following so that the controls are created as desired
this.flowLayoutPanel1.FlowDirection = FlowDirection.TopDown;
this.flowLayoutPanel1.WrapContents = false;
this.flowLayoutPanel1.AutoScroll = true;
Now you can start adding your custom control to this FlowLayoutPanel, either by loop or the way you like. The control will added in linear way, one in each line, and you will also get scroll it it exceeds the given space.
Make sure to define event handler for the control, so that you know when to remove the control. And of course you can set other properties like back groung color etc. That's not going to be any problem.

Add label to textbox custom usercontrol in WinForm

I am writing a windows forms application that has a lot of textboxes. I want to add a label or a caption to the textbox, so that I don’t have to drag a lot labels onto the form and deal with positioning etc. So far I have found 2 possible ways to do this.
Create a user control with the label and textbox. How do I get the
control, label and textbox to size appropriately depending on the
text entered since the control will be reusable and different text sizes will be entered. How to get all the
properties and events of the textbox to remain the same.
Extend a normal textbox and add a string property called label or
caption, and show this property at the left of the textbox. I know
this can be done in Web.UI with CSS but is it possible in a winform
and how?
Any suggestions on how to do either of these?
Thanks.

You can create a UserControl that contains a label and a textbox. When you add the user control to your form, both the label and the textbox within will be added simultaneously. You can expose properties of the label and textbox to assign values at design or run time.
Using this method, you can add multiples of the user control to standardize the layout. As far as resizing the controls based on the text, you'll have to subscribe to events and change the sizing manually.
For example, you can subscribe to the TextChanged event of the label and the textbox. When the event fires, you calculate the size of the string and then adjust the width and position of the controls accordingly.

If you get to the point where you have too many textboxes, I would suggest switching to a DataGridView. The GridView component is very well suited for what you're describing, but of course it requires you to accept a grid layout.
One of the bonuses involved in using a GridView is hard to appreciate until you see it in action: it creates only one HWINDOW at a time (two if you're in editing mode). If you create Labels and TextBoxes all over your form, each one is registered with the operating system as an HWINDOW object. All those HWINDOW objects take time to display! In .NET 1.0, WinForms was so slow that dialogs with more than about two dozen controls were unusable. Even though .NET 2.0 is much better in this regard, but you'll still get significantly better performance by using a single control that manages lots of data, as opposed to lots of controls that each manage one piece of data.
Oh, and another option, if you like: you can also try a PropertyGrid. It has the advantage that it will also show help and allow you to create complex editing controls for each element.

How to draw text at runtime

Basically, Im making a paint application very similar to MSPaint.
The idea is that, that the the user clicks anywhere on the form and should be able to write text in a control. And then following that, that text should be displayed in g.drawstring graphic method.

I don't want to do the whole thing for you, but here is a basic outline of one way to accomplish the goals you outline. This is not necessarily the best way, but it should get you started and will introduce you to a number of WinForms concepts.
Writing the text
Create a Form and add a TextBox control to it. Make sure it is hidden by default. Override the OnMouseClick method of your Form and add code that checks if the TextBox is visible and if not, shows it and puts focus to it for the user to enter their text. If the TextBox is already visible, the code should hide it and create a new UserControl in its place that shows the text (see below for details of that UserControl).
Also add an event handler to the TextBox so that if the user hits Esc, it cancels the edit and if they hit Enter, the text is accepted and the UserControl is created.
Displaying the text
Create a UserControl and make sure that the UserPaint and Opaque styles are set in its construction (see SetStyle - you may also want to consider OptimizedDoubleBuffer and AllPaintingInWmPaint as this can reduce flickering though it does require extra paint code).
Override the OnPaint method in your UserControl and implement the code for drawing the string (remember, you'll also need a way to set the text on the control).
Conclusion
If you hook all that up, you should have something that appears to meet your requirements. For further experimentation, consider how you could remove the need for the UserControl. Good luck and have fun!

Getting handle of Autocomplete dropdown box of textbox in winforms

I wanted to adjust the width of the Autocomplete dropdown box of a textbox. I dont want to adjust the width of that textbox, but only Autocomplete dropdown. I know that there is no way I can increase the width of the Autocomplete dropdown by using properties provided with textbox.
Hence I wanted to know whether there is any way to get the handle of that Autocomplete box and then increase the width of that drop downlist without changing the textbox width?
If this is not possible then I would like to create my custom textbox with autocomplete, in this case how to use the existing autocomplete functionality provided by microsoft? Is there any way to do it. Are there any libraries available for this?

I don't think you can use Microsoft's implementation of autocomplete, which does not have an option to adjust dropdown width.
Create a background thread to not get into the way of typing, and hook up the text change event of a combobox box or a textbox to update the candidate list (assuming autosuggest mode since you mention a dropdown). You can probably add/remove the combobox items on the fly if you have a combobox. But for dropdown list and textbox items you need a popup window
It is easy to get a popup to show, but you need to not use a fixed position so it won't go off the screen when the textbox is close to the edge of the screen. And the focus logic is a little bit complex. you need to keep focus on the textbox unless the user press the arrow keys to make a selection.
so
when focus is on textbox:
arrow keys move the focus to the popup
other keys goes to the textbox, if not handled by the dialog itself, except for the delete key when mouse is over the popup.
when focus is on popup:
arrow keys move the focus to the sibling candidate item or the textbox
other keys goes to the textbox, if not handled by the dialog itself, except for the delete key
mouse clicks:
dismiss the popup outside of the popup or the popup.
update the value of textbox if a candidate item in the popup is clicked on
It takes a lot of effort to get the focus/threading right. If you can afford some form space, you can just add a fixed width listbox to the form instead, like Visual Studio help viewer's index pane.

After going through lot of blog posts and different articles, I came to a consensus that it is next to impossible to get a solution to my problem in the way I wanted. So I've decided either to come up with a custom solution or as Sheng Jiang said I need to implement my own autocomplete object.
I've come up with a solution which fits my requirement by increasing the width of the textbox as per the largest string in the autocomplete string list while I'm adding the autocomplete custom source. As I said I cant increase the width of the text box because of the size constraint on the form, so I decided to keep this textbox in a panel and increase the size of the textbox inside that. Panel will not grow with the textbox so that solved my problem.
I know this is not perfect solution but it fits my requirement.