[c#] How to read text files with ANSI encoding and non-English letters?

I have a file that contains non-English chars and was saved in ANSI encoding using a non-English codepage. How can I read this file in C# and see the file content correctly?

Not working

StreamReader sr=new StreamReader(@"C:\APPLICATIONS.xml",Encoding.ASCII);
var ags = sr.ReadToEnd();
sr=new StreamReader(@"C:\APPLICATIONS.xml",Encoding.UTF8);
ags = sr.ReadToEnd();
sr=new StreamReader(@"C:\APPLICATIONS.xml",Encoding.Unicode);
ags = sr.ReadToEnd();

Working but I need to know what is the code page in advance, which is not possible.

sr=new StreamReader(@"C:\APPLICATIONS.xml",Encoding.GetEncoding(1252));
ags = sr.ReadToEnd();

If I remember correctly the XmlDocument.Load(string) method always assumes UTF-8, regardless of the XML encoding. You would have to create a StreamReader with the correct encoding and use that as the parameter.

xmlDoc.Load(new StreamReader(
                     File.Open("file.xml"), 
                     Encoding.GetEncoding("iso-8859-15"))); 

I just stumbled across KB308061 from Microsoft. There's an interesting passage: Specify the encoding declaration in the XML declaration section of the XML document. For example, the following declaration indicates that the document is in UTF-16 Unicode encoding format:

<?xml version="1.0" encoding="UTF-16"?>

Note that this declaration only specifies the encoding format of an XML document and does not modify or control the actual encoding format of the data.

Link Source:

XmlDocument.Load() method fails to decode € (euro)

You get the question-mark-diamond characters when your textfile uses high-ANSI encoding -- meaning it uses characters between 127 and 255. Those characters have the eighth (i.e. the most significant) bit set. When ASP.NET reads the textfile it assumes UTF-8 encoding, and that most significant bit has a special meaning.

You must force ASP.NET to interpret the textfile as high-ANSI encoding, by telling it the codepage is 1252:

String textFilePhysicalPath = System.Web.HttpContext.Current.Server.MapPath("~/textfiles/MyInputFile.txt");
String contents = File.ReadAllText(textFilePhysicalPath, System.Text.Encoding.GetEncoding(1252));
lblContents.Text = contents.Replace("\n", "<br />");  // change linebreaks to HTML

using (StreamWriter writer = new StreamWriter(File.Open(@"E:\Sample.txt", FileMode.Append), Encoding.GetEncoding(1250)))  ////File.Create(path)
        {
            writer.Write("Sample Text");
        }