SelectSingleNode C# XML Example

C# > XML > SelectSingleNode

SelectSingleNode selects the first node that matches the XPath expression.

Example

Select node based on attribute value

Products.xml

xml version='1.0'?>

<products xmlns="urn:products-schema">
  <product name="Product1">
    <price>100</price>
  </product>
  <product name="Product2">
    <price>200</price>
  </product>
</products>

C# Code

XmlDocument doc = new XmlDocument();

doc.Load(@"D:\Products.xml");

XmlNamespaceManager nsmgr = new XmlNamespaceManager(doc.NameTable);
nsmgr.AddNamespace("pp", "urn:products-schema");

XmlElement root = doc.DocumentElement;

XmlNode product = root.SelectSingleNode("pp:product[@name='Product1']", nsmgr);

C# XML Examples

C# > XML

XML is Extensible Markup Language is a markup language. It defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. (read more on http://en.wikipedia.org/wiki/XML)

The System.Xml namespace provides standards-based support for processing XML.




Classes

• XmlDocument
• XmlWriter

Examples

• Create CDATA section
• SelectSingleNode returns null
• SelectSingleNode
• AppendChild

Why SelectSingleNode always returns null?

C# > XML > XmlNamespaceManager > SelectSingleNode null

Why SelectSingleNode always returns null?

Because is missing the XML namespace defined SelectSingleNode call.

Solution:

XmlDocument doc = new XmlDocument();

doc.Load(xmlfile);

XmlNamespaceManager nsMgr = new XmlNamespaceManager(doc.NameTable);

nsMgr.AddNamespace("ns", "urn:www.data.com/feed");

var node = doc.SelectSingleNode("ns:ParentNode/ns:ChildNode", nsMgr);

OLE DB is an API for accessing data.

C# > Data > OLE DB

OLE DB is an API for accessing data. It is common to access Microsoft Access databases, or Microsoft Excel spreadsheets.

Examples:

• Get list of tables Microsoft Access

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!