Trying to get a XML value and compare with a string value C#

Question

Hi I'm a little bit lost with xml.

I try to get a value from an xml located on my github, then I want to compare the value with the string value of "LPEVersionCust".

On github I add a xml file to my repo

<?xml version="1.0" encoding="utf-8"?>
<Definition>
        <Version name="0.0.2" />
</Definition>

On my winforms (MainForm.cs)

private string LPEVersionCust = "0.0.1";
private string LPEUrlPathX = "https://raw.githubusercontent.com/username/myrepo/main/lpeCL.xml"; //not the real address

So I try:

using System;
using System.Windows.Forms;
using System.Diagnostics;
using System.IO;
using System.Xml;
using System.Reflection;

namespace LPEApp
{
    public partial class mainApp : Form
    {
        private string LPEUrlPathX = "https://raw.githubusercontent.com/username/myrepo/main/lpeCL.xml";
        private string LPEInstVersionCust= "0.0.1";
        
        
        public mainApp()
        {
            InitializeComponent();
        }
        
        private void mainApp_Load(object sender, EventArgs e)
        {
            GetUpdateLPEVersion();
        }
        
        private void GetUpdateLPEVersion()
        {
            try
            {
                XmlDocument GetLPEVersion = new XmlDocument();
                GetLPEVersion.Load(LPEUrlPathX);
                XmlNodeList lpnodes = GetLPEVersion.DocumentElement.SelectNodes("/Definition");
                
                foreach (XmlNode node in lpnodes)
                {
                    string LPEVersion = node.Attributes[1].Value;
                }
                double LPEVersionCust = double.Parse(LPEInstVersionCust);

                if (LPEVersion > LPEVersionCust)
                {
                    // Error message CS0103 : The name 'LPEVersion' does not exist in the current context

                }

            }
            catch (Exception)
            { }

        }
   }
}

Answer 1

In your code you have defined LPEVersion in a scope that doesn't exist outside of the foreach loop.

It's like writing this:

{
    string name = "Foo";
}

Console.WriteLine(name);

You get the same error.

You need the definition of LPEVersion in the same scope you're trying to use it in.

---

You probably need some sort of code like this to do your comparison of versions:

private void GetUpdateLPEVersion()
{
    string versionText = XDocument.Load(LPEUrlPathX).Root?.Element("Version")?.Attribute("name")?.Value;
    if (Version.TryParse(versionText, out Version version))
    {
        var custom = Version.Parse(LPEInstVersionCust);
        if (version.CompareTo(custom) == 1)
        {
            // You have a newer version.
        }
    }
}

Answer 2

The string LPEVersion variable is scoped to the foreach loop.

foreach (XmlNode node in lpnodes)
{
    string LPEVersion = node.Attributes[1].Value;
    double LPEVersionCust = double.Parse(LPEInstVersionCust);
    if (LPEVersion > LPEVersionCust)
    {
        //Do something
    }
}

This should work.

Note you probably don't want to parse LPEInstVersionCust every iteration.

Answer 3

C# has a System.Version API that you can use for parsing version string values and comparing them.

You can alter your current application to do this.

using System;
using System.Windows.Forms;
using System.Diagnostics;
using System.IO;
using System.Xml;
using System.Reflection;

namespace LPEApp
{
    public partial class mainApp : Form
    {
        private string LPEUrlPathX = "https://raw.githubusercontent.com/username/myrepo/main/lpeCL.xml";
        private Version LPEInstVersion = new Version("0.0.1");

        public mainApp()
        {
            InitializeComponent();
        }

        private void mainApp_Load(object sender, EventArgs e)
        {
            GetUpdateLPEVersion();
        }

        private void GetUpdateLPEVersion()
        {
            try
            {
                XmlDocument GetLPEVersion = new XmlDocument();
                GetLPEVersion.Load(LPEUrlPathX);
                XmlNodeList lpnodes = GetLPEVersion.DocumentElement.SelectNodes("/Definition");

                foreach (XmlNode node in lpnodes)
                {
                    Version LPEVersion = new Version(node.Attributes[1].Value);

                    if (LPEVersion > LPEInstVersion)
                    {
                        // Do thing
                    }
                }
            }
            catch (Exception) { }
        }
    }
}

This works as long as you are certain that the node.Attributes[1].Value is definition a version number. If not, you may want to use Version.TryParse instead to ensure that the version number is correct.

Answer 4

I found a way

What I did and it works...

I changed my xml file to:

<?xml version="1.0" encoding="utf-8"?>
<LPEDefinition>
    <Version>0.0.1</Version>
</LPEDefinition>
    

And in MainForm.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Linq.Expressions;
using System.Xml.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Diagnostics;
using System.IO;
using System.Xml;
using System.Reflection;
using System.Text.RegularExpressions;
using System.Configuration;

namespace LPEApp
{
    public partial class mainApp : Form
    {
        private string LPEInstVersionCust = "0.0.0";
        private string LPEVersionAvailable = "";
        
        public mainApp()
        {
            InitializeComponent();
        }

        private void mainApp_Load(object sender, EventArgs e)
        {
            GetUpdateLPEVersion();
        }

        private void GetUpdateLPEVersion()
        {
            XmlDocument GetLPEVersion = new XmlDocument();
            GetLPEVersion.Load("https://raw.githubusercontent.com/.../.../main/lpeCL.xml");
            XmlNode root = GetLPEVersion.DocumentElement.SelectSingleNode("/LPEDefinition");
            foreach (XmlNode modXml in root.ChildNodes)
            {
                string ver = modXml.Attributes["name"].InnerText;
                LPEVersionAvailable = ver;
                
                if (LPEVersionAvailable != LPEInstVersionCust)
                {
                    DialogResult dr = MessageBox.Show("There is a new version available....", "... is out dated", MessageBoxButtons.YesNo);
                    if (dr == System.Windows.Forms.DialogResult.Yes)
                    {
                        Process.Start("https://github.com/.../.../releases/latest");
                    }
                }
            }
        }
    }
}

Thanks for your helps!