Snap it! - How to Take a Screen Shot Using .NET

Introduction

We all would have used snap shots (screen shots) to illustrate bugs or behavior or something that others could understand by seeing them. For taking snap shots we just hit the "Print Screen" key and copy it to Ms Paint and save it. Ever wondered how to programmatically take a snap shot? Then this article is for you.



Image-1 This is how the application looks

Scenario

Why do we need to take snapshots programmatically? Consider a scenario where you want to report some kind of behavior errors in an application. Human supervision is not possible when the occurrence of error is random. So we just code a program to take snap shots at regular intervals and store it as a image file. So that later you can use it.

GDI classes we need to know

Lets see what we need to know before we do coding. We need to have a little knowledge about GDI and graphics classes. The Graphics class provides methods for drawing objects to the display device. A Graphics object is associated with a specific device context. This class is used as a canvas to draw images. In order to display anything in a window, you have to obtain a reference to the window's Graphics object.

Next comes the Bitmap class. A Bitmap object is an object used to work with images defined by pixel data. A bitmap consists of the pixel data for a graphics image and its attributes.

Getting Started

To use the GDI classes we need to include System.Drawing.Imaging namespace in the "using" section of the code. Go to the source view and add a string variable and a property to the class. This string variable is used in the property to store and retrieve the output file name.

// variable to store output file name
private string strFilename;

// Property for storing and retrieving output file name
public string filename
{
get{return strFilename;}
set{strFilename=value;}
}

In the design view, add a button and a savefiledialog to the form. Double click the button and go to the click event in the code view. Use the savefiledialog control to retrieve the output file name from the user. And store the file name in the variable strFilename using the property filename.

}

Before taking the snap shot we hide our application because we don't want our application in the snap shot image. Sometimes even after hiding the application, the snap shot pictures our application, this is because the application takes few extra milliseconds to hide, so we make our application to wait for some milliseconds.