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How to fill part of the graphical figure

So, I have some simple figure (circle, ellipse, rectangle of closed polygon) and I need to fill only part of it.
I mean, I have GraphicsPath or similar object (set of points) and now I can simply fill the whole figure with, for example, orange color.
What I need: user enters 25% and I fill only 25% of the figure, starting from some side (top/bottom).
Maybe, it will be nessesary to find some sub-figure or (bad idea, I know) check all the points in on the field and fill them (only those which inside figure) one by one untill their amount will be 1/4 from the area of the figure. But it won't be so fast especially when image is about 5-6000 pixels from one side.
Here's sample what I have now and what I need for 25%. Important: instead of 25% can be any value.
Project: C# .net 3.5 WinForms
UPD:
Basic usecase.
User draws a figure (circle, ellipse, rectangle, polygon)
User enters value from 0 to 100 (percents)
I fill figure from bottom to the top until I filled amount of area (!), which is equal to user's value
I'm open for any ideas even without code.

Dynamical rectangle plot c# wpf

I want to create a plot that dynamically displays active elements as rectangles. I have achieved a first version that is actually ok using OxyPlot.Annotations.RectangleAnnotation which I add to myPlotModel.Annotations, you can see it in the image hereafter:
Example of wanted display
The thing is that after a while, the amount of drawn rectangles make the update not smooth as I update the shown timewindow (which is set to 15 seconds). I have already set a maximum of drawn elements that suffice to cover the displayed window (i.e. the rectangles get removed as they are too far in the past), but the rendering is still jerky. I draw the rectangles by allocating them to an equal fraction of the Y-axis, that is the third one from the top gets:
rowNumber= 3.0
minimumY = maximalY - maximalY / totalElements * rowNumber
maximumY = maximalY - maximalY / totalElements * (rowNumber + 1.0)
And the Y-axis is hidden.
My question:
Is there a smarter way of creating such a display that would be less computationally heavy, and therefore allow a smoother update? I do not have to stick to OxyPlot, it is simply the easiest way that I found to obtain what I wanted.
Thanks for your answers!

Technically, the answer to your question is "Yes".
There are a number of ways to do this.
You could have a vertical itemscontrol that had an itemscontrol in it's template. That could have a canvas as it's itemspresenter and you could bind canvas.top and canvas.left to properties in it's content. Template each into a rectangle and bind height and width.
And of course do something about the scale on the bottom and the column of activity labels or whatever you want to call them there.
Unless you're using an absolutely ancient machine, that'd just fly.
It's quite a lot of work but it would probably be quicker to write that than to search through a load of alternative packages and decide which was optimal.

Draw a graph using arrays of pictureboxes

I am currently writing a program where I need to draw some graph's. I need to have a little bit specific layout in these graphs. For example I have three stages of a length in days defined by the user. a start stage of for example 30 days, a mid stage of 40 and an end stage of 20 days. These stages I want to have all a different backgroundcolor in the graph. I do that by drawing pictureboxes and adapting their widths to the stage lengths. Also for every day in the total length I want to draw a vertical line and for the amount of horizontal lines in the graph I take the maximum of y = f(x).
y = f(x) needs to be plotted on the graph. For I use many pictureboxes on the background I cannot use the graphics.DrawLine for it will be drawn behind the pictureboxes. So I decided to make the line with an array of pictureboxes ;) It works fine, but obviously it takes a lot of time to load the program now.
Is there another way to draw this graph using arrays of controls that require less effort from the computer? Or should I completely stop with the arrays?
(I wanted to post my picture here, but I don't have ten reputation yet because I'm a noobie :( )
Later on I will add more lines to this graph, but since I figured that my program is already slowing down I ceased programming those other lines and went to the all-knowing forum!
Any help will be much appreciated!
Greetz,
Arrie

The common form controls aren't really suitable for this purpose. I'd suggest taking a look at using libraries that give you more power and control over visuals and graphics.

#Kári is right:
If you want to stay with .NET only (no 3rd library dependence) you can use GDI. In .NET you can use by including System.Drawing.dll as an reference.
One simple yet correct approach would be:
create a target control (picturebox for example)
implement the OnPaintDraw Event which gives you an Graphics object
that contains many drawing methods. See MSDN for more information:
MSDN -> Graphics
The methods of Graphics will always draw above the control, so make sure your target control is visible an not behind any other control.
If GDI is not enough you can check out other libraries. (See .NET graph library around?)

How to render dynamic data in a custom WPF control, such as a line graph?

I'm working on a LineGraph control which consists many DependencyProperties that affect how the control should display its data. For example, the control contains the following properties to affect its axes:
AxisStroke - Color of the axes.
AxisThickness - Stroke thickness of the axes.
It also contains properties for display numbers & tick marks
VerticalTicks - True/False to indicate whether or not ticks appear along the vertical axis
HorizontalTicks - True/False to indicate whether or not ticks appear along the horizontal axis
VerticalMin - Minimum value on the vertical axis (numeric)
VerticalStep - The distance in between each vertical tick
VerticalMax - Maximum value on the vertical axis (numeric)
HorizontalMin - Minimum value on the horizontal axis (numeric)
HorizontalStep - The distance in between each horizontal tick
HorizontalMax - Maximum value on the horizontal axis (numeric)
And many more properties exist to allow for different line styles on a single graph (LineColor, LineThickness, DataPointShape, and DataPointIcon to name a few).
My goal is to be able to call out my LineGraph in XAML to insert it into a Window. I would like to be able to specify each of these settings inside the XAML as well, and see the new rendered image of the control in the WPF designer.
Now, given there is a lot of geometric shapes to render on the LineGraph, I though using a Canvas would be a good choice to render the data. Unfortunately, when I'm working in XAML, I cannot perform computations for the locations of shapes based on the control's width & height.
And yes, the shapes' locations must be computed because the data points for the graph are dynamic and the tick-related information is dynamic. Not to mention, I would like to display the actual values along each axis of the LineGraph.
So, I thought I might be able to display this control as if I was doing the rendering in C# code. Other windowing frameworks sometimes provide a Render method that can be used for laying out all of the sub-components.
Doing this, however, doesn't seem possible since WPF relies heavily on XAML for the visual appearance of controls. Also, requiring that the WPF designer must display the LineGraph based on the properties and data specified, it doesn't seem like C# code would solve the problem.
I suppose my questions are these:
How can I render data dynamically inside of a WPF control?
Am I able to specify in C# how my control is rendered, allowing the WPF designer to reflect it?
Side Note:
I've done quite a bit of research, but I am only finding information on how to implement more simple types of controls. If you know of any references that contain information on this topic, please feel free to post them in addition to your answers. I will be more than happy to learn how to do this completely.
EDIT:
I've created a graph using Excel to elaborate what the LineGraph control might look like if it has correct data and properties.

I will answer this based on my experience on implementing custom built graphing libraries in WIN32, WinForm, WPF, WinCE, WP8+WinRT, ....and even on a FPGA :)
It's extremely difficult to implement one from scratch. It may seem easy at first but you will run into a lot of "What should I do if this happens?". For example, in your above graph it seems you got a DataPoint # (5,100) it graphs it pretty well. But lets say, I add another DataPoint # (5.000000005, 0). How would you handle that in your code? Would you say that each pixel on the graph represents an exact value on the X-Axis, or does each pixel represent a range of X-Values?
I would recommend that you use an already establish library to do what you want to do unless you need something very specific like lets say you need horizontal cursors on the graph (think Tektronix Oscilloscope) and you need to calculate some values in between the two cursors.. then maybe you need to implement your own custom one or build on top of an open source one.
So, if you are still adamant of creating your own custom control here are answers to your questions.
How can I render data dynamically inside of a WPF control?
You can use a WriteableBitmap and create your own primitive drawing library from that. After you're done rendering, set it as the ImageSource of your control.
Or you can use WriteableBitmapEx which has GDI like drawing functions already implemented for you.
WriteableBitmapEx CodePlex Page, I also think you can just get it from NuGet as well.
You can also use a <Canvas> and add UI elements to that as well.
Am I able to specify in C# how my control is rendered, allowing the WPF designer to reflect it?
This depends on how you create your controls, but yes you can create Properties in your custom control that will appear in the Designer. Allowing you to change it thus updating the display. I would read a lot of tutorials about writing your own custom user control library. They can explain it better than I can in a SO answer. If you implement the properties correctly it should like so.....
Full Size Image: http://i.stack.imgur.com/pmevo.png
After changing the Number of Rows from 15 to 10 and the starting Y offset to -1 (thus moving the graph up and making the rows a lot taller)
Full Size Image: http://i.stack.imgur.com/0RKnA.png

.NET Chart control - dynamically change y-axis interval

I have a bar graph displaying a number of different series (stacked on each other) and I'm trying to find a way to dynamically change the y-axis interval if the values go above a set value.
If the bars only go up to a maximum of 50, I'd like the interval to be 25 so the bars still 'look' rather small. But if a large spike comes through, the interval needs to be set to 0 so the large spike is more noticeable.
Oh, and this is in C# .NET 3.5
I hope that makes sense :)
Thanks in advance

This is pretty much feasible by tweaking both the size of the axis and the relative intervals dynamically by updating the right properties. Default control behavior is rescaling the axis to adapt to the dataset so this should be no problem (works well for me)
Take a look at the Axis Class MSDN Reference, especially the Interval and IntervalAutoMode Properties. (the MSDN in pretty exhaustive on chart control if you dig enough you'll find everything you might need).
besides I HEAVILY advice you to download the very complete sample application
and play around with it locally. It is pretty exhaustive and you'll have the complete source at hand.

Set IntervalAutoMode="Variable Count" and dint mention any axis interval in the Axis Y element of the chart Area of that chart,it will adjust according to the maximum value.