C# ComponentModel

C# > System > ComponentModel

ComponentModel provides classes that are used to implement the run-time and design-time behavior of components and controls.

• BackgroundWorker Example
• CancelEventHandler
• DataAnnotations

BackgroundWorker and progress bar C# example

C# > System > ComponentModel > BackgroundWorker

The BackgroundWorker runs an operation on a separate and dedicated thread.
Time-consuming operations can cause the user interface (UI) to seem as frozen and stop responding while they are running.
BackgroundWorker class represents a solution to this.






Example

Use BackgroundWorker and progress bar to display a progress of import operation

using System;

using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.OleDb;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Forms;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace BackgroundWorker 

{
    

    /// Interaction logic for MainWindow.xaml
    ///

    public partial class MainWindow : Window

    {
        private BackgroundWorker worker = null;
        public MainWindow()
        {        
        }
        void worker_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {          
            pBar.Value = e.ProgressPercentage;
            lblStatus.Content = "Processing......" + pBar.Value.ToString() + "%";
        }
        private void worker_DoWork(object sender, DoWorkEventArgs e)
        {
            // do your task here
            for (int i = 0; i <= 100; i++)
            {
                Thread.Sleep(500);
                if (worker == null)
                    break;
                worker.ReportProgress(i);
            }
        }
        private void worker_RunWorkerCompleted(object sender,RunWorkerCompletedEventArgs e)
        {
            lblStatus.Content = "Task finished";
        }
        private void Button_Click(object sender, RoutedEventArgs e)
        {
            if (worker == null)
            {
                worker = new BackgroundWorker();
                worker.DoWork += worker_DoWork;
                worker.RunWorkerCompleted += worker_RunWorkerCompleted;
                worker.ProgressChanged += worker_ProgressChanged;
                worker.WorkerReportsProgress = true;
                worker.WorkerSupportsCancellation = true;
            }
            if (worker.IsBusy != true)
            {
                // Start the asynchronous operation.
                worker.RunWorkerAsync();
            }
        }
        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            pBar.Maximum = 100;
        }
        private void btnCancel_Click(object sender, RoutedEventArgs e)
        {
            worker.CancelAsync();
            worker = null;
        }
    }
}

Parentheses () Operator C# Example

C# > Operators > () Operator

Parentheses operator is used for

1. Casting

double a = 4.5;
int b;
a = (int)q; // Cast double to int   
2. Invoke

Method(); // Call method

Note: This operator cannot be overloaded!

Predicate Delegate C# Example

C# > System > Predicate<T> Delegate

This delegate is used to search for elements in the collection.
Predicate<T> delegate is represented by a lambda expression.

Example

public class Student

{
       public string Name { get; set; }
       public int Year { get; set; }
       public Student(string name, int year)
       {
              this.Name = name;
              this.Year  = year;
       }
}

List<Student> groups = new List<Student>();

groups.AddRange(new Student[] { new Student("Stud1", 1973),
                                new Student("Stud2", 2000),
                                new Student("Stud3", 2010),
                                new Student("Stud4", 1999),
                                new Student("Stud5", 1995) });

foreach (var g in groups.FindAll(x => x.Year >= 2000))

              System.Windows.MessageBox.Show(g.Name);

  

C# System Interfaces

C# > System > Interfaces

• IEquatable
• ICloneable

IEquatable C# Example

C# > System > Interfaces > IEquatable

IEquatable<T> Interface defines Equals method for determining equality of instances.

Example

public class Car : IEquatable<Car>

{
            public int Power { get; set; }
       public bool Equals(Car other)
       {
              if (other == null)
                    return false;
              if(this.Power == other.Power)
                    return true;
              return false;
       }
       public override bool Equals(Object obj)
       {
              if (obj == null)
                    return false;
              Car carObj = obj as Car;
              if (carObj == null)
                    return false;
              else
                    return Equals(carObj);
       }  
}

Car c1 = new Car();
c1.Power = 100;
Car c2 = new Car();
c2.Power = 100;
if (c1.Equals(c2))
    System.Windows.MessageBox.Show("Same power");

Identify feature DotSpatial Map

DotSpatial > Controls > Map

Identify feature DotSpatial Map on MouseUP event.

private void map1_MouseUp(object sender, MouseEventArgs e)

{
      Coordinate cor =  map1.PixelToProj(e.Location);
      Extent ex = new Extent(cor.X, cor.Y, cor.X, cor.Y);
      var  mLayer = map1.Layers[0];
      IFeatureLayer il = (IFeatureLayer) mLayer;
      List<IFeature> result = il.DataSet.Select(ex);
      if (result.Count>0) 
      {
           IFeature ift = result.FirstOrDefault();
           MessageBox.Show(ift.DataRow[0].ToString());
       }
}