Application.DoEvents Method in C#.NET

It Shows the description for the working of Application.DoEvents in C#.NET

It Processes all Windows messages currently in the message queue.

Namespace:  System.Windows.Forms
Assembly:  System.Windows.Forms (in System.Windows.Forms.dll)

‘Declaration

Application.DoEvents();

When you run a Windows Form, it creates the new form, which then waits for events to handle. Each time the form handles an event, it processes all the code associated with that event. All other events wait in the queue. While your code handles the event, your application does not respond. For example, the window does not repaint if another window is dragged on top.

If you call DoEvents in your code, your application can handle the other events. For example, if you have a form that adds data to a ListBox and add DoEvents to your code, your form repaints when another window is dragged over it. If you remove DoEvents from your code, your form will not repaint until the click event handler of the button is finished executing. 

Caution

Calling this method causes the current thread to be suspended while all waiting window messages are processed. If a message causes an event to be triggered, then other areas of your application code may execute. This can cause your application to exhibit unexpected behaviors that are difficult to debug. If you perform operations or computations that take a long time, it is often preferable to perform those operations on a new thread. For more information about asynchronous programming,

lists of the important classes and enumerations in theSystem.Drawing.Drawing2D namespace.

Graphics and Graphics paths 

The GraphicsState and GraphicsContainer classes report information about the current Graphics object. GraphicsPath classes represent a series of lines and curves. The GraphicsPathIterator and PathData classes provide detailed information about the contents of a GraphicsPath object.

Matrix and transformation related types

The Matrix class represents a matrix for geometric transforms. The MatrixOrder enumeration specifies the order for matrix transformations.

Brush classes

The PathGradientBrush and HatchBrush classes enable you to fill shapes with either a gradient, or hatch pattern, respectively.

Enumeration related to lines

The LineCap and CustomLineCap enumerations enable you to specify cap styles for a line. The, LineJoin enumeration enables you to specify how two lines are joined in a path. The PenAlignment enumeration enables you specify the alignment of the drawing tip, when you draw a line. The PenType enumeration specifies the pattern a line should be filled with.

Enumerations related to filling shapes and paths

The HatchStyle enumeration specifies fill styles for a HatchBrush. The Blend class specifies a blend pattern for a LinearGradientBrush. The FillMode enumeration specifies the fill style for a GraphicsPath.

Classes

---

	Class	Description
	AdjustableArrowCap	Represents an adjustable arrow-shaped line cap. This class cannot be inherited.
	Blend	Defines a blend pattern for a LinearGradientBrush object. This class cannot be inherited.
	ColorBlend	Defines arrays of colors and positions used for interpolating color blending in a multicolor gradient. This class cannot be inherited.
	CustomLineCap	Encapsulates a custom user-defined line cap.
	GraphicsContainer	Represents the internal data of a graphics container. This class is used when saving the state of a Graphics object using the BeginContainer and EndContainer methods. This class cannot be inherited.
	GraphicsPath	Represents a series of connected lines and curves. This class cannot be inherited.
	GraphicsPathIterator	Provides the ability to iterate through subpaths in a GraphicsPath and test the types of shapes contained in each subpath. This class cannot be inherited.
	GraphicsState	Represents the state of a Graphics object. This object is returned by a call to the Save methods. This class cannot be inherited.
	HatchBrush	Defines a rectangular brush with a hatch style, a foreground color, and a background color. This class cannot be inherited.
	LinearGradientBrush	Encapsulates a Brush with a linear gradient. This class cannot be inherited.
	Matrix	Encapsulates a 3-by-3 affine matrix that represents a geometric transform. This class cannot be inherited.
	PathData	Contains the graphical data that makes up a GraphicsPath object. This class cannot be inherited.
	PathGradientBrush	Encapsulates a Brush object that fills the interior of a GraphicsPath object with a gradient. This class cannot be inherited.
	RegionData	Encapsulates the data that makes up a Region object. This class cannot be inherited.

Enumerations

---

	Enumeration	Description
	CombineMode	Specifies how different clipping regions can be combined.
	CompositingMode	Specifies how the source colors are combined with the background colors.
	CompositingQuality	Specifies the quality level to use during compositing.
	CoordinateSpace	Specifies the system to use when evaluating coordinates.
	DashCap	Specifies the type of graphic shape to use on both ends of each dash in a dashed line.
	DashStyle	Specifies the style of dashed lines drawn with a Pen object.
	FillMode	Specifies how the interior of a closed path is filled.
	FlushIntention	Specifies whether commands in the graphics stack are terminated (flushed) immediately or executed as soon as possible.
	HatchStyle	Specifies the different patterns available for HatchBrush objects.
	InterpolationMode	The InterpolationMode enumeration specifies the algorithm that is used when images are scaled or rotated.
	LinearGradientMode	Specifies the direction of a linear gradient.
	LineCap	Specifies the available cap styles with which a Pen object can end a line.
	LineJoin	Specifies how to join consecutive line or curve segments in a figure (subpath) contained in a GraphicsPath object.
	MatrixOrder	Specifies the order for matrix transform operations.
	PathPointType	Specifies the type of point in a GraphicsPath object.
	PenAlignment	Specifies the alignment of a Pen object in relation to the theoretical, zero-width line.
	PenType	Specifies the type of fill a Pen object uses to fill lines.
	PixelOffsetMode	Specifies how pixels are offset during rendering.
	QualityMode	Specifies the overall quality when rendering GDI+ objects.
	SmoothingMode	Specifies whether smoothing (antialiasing) is applied to lines and curves and the edges of filled areas.
	WarpMode	Specifies the type of warp transformation applied in a Warp method.
	WrapMode	Specifies how a texture or gradient is tiled when it is smaller than the area being filled.

Make a countdown timer in C#.NET

This example shows how to make a countdown timer in C#.NET

Keywords: countdown timer, timer, alarm, CSharp.NET, C#.NET

If you enter a duration in the format h:mm:ss and click the button, the following code converts your text into a TimeSpan and adds it to the current time. It saves the result in m_StopTime and enables the timer1 timer.

private void button1_Click(object sender, EventArgs e)

        {

            TimeSpan duration = TimeSpan.Parse(textBox1.Text);

            m_StopTime = DateTime.Now.Add(duration);

            

           timer1.Enabled = true;

        }

When the timer fires, it calculates the difference between the current time and the desired stop time and displays the time remaining in the label lblRemaining. Then if the total seconds remaining is zero, the program maximizes its form and makes its form topmost so it appears above all other forms, hopefully attracting your attention.

private void timer1_Tick(object sender, EventArgs e)

        {

            TimeSpan remaining = m_StopTime.Subtract(DateTime.Now);

            remaining = new TimeSpan(remaining.Hours, remaining.Minutes, remaining.Seconds);

            if (remaining.TotalSeconds < 0)

                remaining = TimeSpan.Zero;

            label1.Text = remaining.ToString();

            if (remaining.TotalSeconds <= 0)

            {

                this.WindowState = FormWindowState.Maximized;

                this.TopMost = true;

                timer1.Enabled = false;

            }

        }

 

Here the full code.

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Windows.Forms;

namespace testc

{

    public partial class Form1 : Form

    {

        System.DateTime m_StopTime = default(System.DateTime);

        public Form1()

        {

            InitializeComponent();

        }

        private void Form1_Load(object sender, EventArgs e)

        {

        }

        private void button1_Click(object sender, EventArgs e)

        {

            TimeSpan duration = TimeSpan.Parse(textBox1.Text);

            m_StopTime = DateTime.Now.Add(duration);

            

           timer1.Enabled = true;

        }

        private void timer1_Tick(object sender, EventArgs e)

        {

            TimeSpan remaining = m_StopTime.Subtract(DateTime.Now);

            remaining = new TimeSpan(remaining.Hours, remaining.Minutes,

                remaining.Seconds);

            if (remaining.TotalSeconds < 0)

                remaining = TimeSpan.Zero;

            label1.Text = remaining.ToString();

            if (remaining.TotalSeconds <= 0)

            {

                this.WindowState = FormWindowState.Maximized;

                this.TopMost = true;

                timer1.Enabled = false;

            }

        }

    }

}