C# Saving into an XML document

Question

I try to save an object to an XML Document. I always get an inner Exception Error. I think it has to do something with boxing and unboxing but i cannot help myself.

So here we go:

The Method for XML Saving

public class Saveclass
//
        public static void Save(string filename, List<Class> classlist)
        {

            StreamWriter writer = new StreamWriter(filename, false, Encoding.UTF8);
            XmlSerializer serializer = new XmlSerializer(typeof(class));
            serializer.Serialize(writer,classlist);//Here i get the error at classlist
            writer.Close();
        }

And here the SaveFile Dialog

private void SaveButton(object sender, EventArgs e)
        {
            SaveFileDialog dialog = new SaveFileDialog();

            dialog.Filter = "XML Data|*.xml";
            if (dialog.ShowDialog() == DialogResult.OK)
            {
                List<class> classlist = null;
                foreach (ListViewItem item in this.listViewWinforms.Items)
                {
                    classlist = new List<class>();
                }
                Saveclass.Save(dialog.FileName, classlist)
            }
        }

In the Basic i have a Listview with Items inside and want to save these Items in my listview to an XML Document Error is

System.InvalidOperationException: 'Trying to generate an XML Document

InvalidCastException: The object of the Type "System.Collections.Generic.List`1[Namespace.Class]" cannot cast into"Namespace.Class"

Any time you “get the error” you need to tell us what the error is. — Dour High Arch
– Dour High Arch, Commented Dec 1, 2019 at 19:56
@DourHighArch i editet it. So you can see the error. I think it has to do with boxing and unboxing — ddave
– ddave, Commented Dec 1, 2019 at 20:24

user1348592 · Accepted Answer · 2019-12-01 20:44:34Z

2

There is a type mismatch.

You are defining your serializer as:

new XmlSerializer(typeof(class));

Which is configured to serialize objects of type class.

However, you are then trying to serialize the classlist object, which is not a class but a List<Class>.

Try defining your serializer as:

new XmlSerializer(typeof(List<Class>));

By the way, naming your class class is very confusing. You should try to name your classes more descriptively.

answered Dec 1, 2019 at 20:44

user1348592

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Comments

richardsonwtr · Accepted Answer · 2019-12-01 21:02:23Z

I think you need to change just one line:

Just use typeof(List) instead of typeof(class))

XmlSerializer serializer = new XmlSerializer(typeof(List<Class>));

Here is a small example

using System;
using System.Collections.Generic;
using System.Text;
using System.Xml.Serialization;
using System.IO;

namespace ConsoleApplication1
{
    public class Program
    {
        public static void Main(string[] args)
        {
            List<Car> myList = new List<Car>();
            myList.Add(new Car(){ Name = "Beetle", Brand = "VW", Price = 5999.9M });
            myList.Add(new Car(){ Name = "Corolla", Brand = "Toyota", Price = 49999.9M });

            Saveclass.Save("carlist.xml",myList);
        }
    }

    public static class Saveclass
    {
        public static void Save(string filename, List<Car> classlist)
        {
            StreamWriter writer = new StreamWriter(filename, false, Encoding.UTF8);
            XmlSerializer serializer = new XmlSerializer(typeof(List<Car>));
            serializer.Serialize(writer,classlist);
            writer.Close();
        }
    }

    public class Car
    {
      public string Name  {get;set;}
      public string Brand  {get; set;}
      public decimal Price {get; set;}
    }
}

You can test here

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