how to fix Xamarin.forms System.IO.FileNotFoundException: Could not find file

问题

I am using xamrin.forms, and I am trying to access file and read it.

I have lastusername.txt as text file and I set the build action for it as "Content", actually I am trying to read file as the following:

  var filename = System.IO.Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Personal), "lastusername.txt");
    if (filename != null)
           return System.IO.File.ReadAllText(filename);//error occurred here 
    else
           return "";

I get the following Error:

System.IO.FileNotFoundException: Could not find file

回答1:

Place your file within the Android Assets folder and assign it with a build type of "AndroidAsset".

Since your app's assets are read-only, you can then read it via the AssetManager, saving (copy) it somewhere else if it does not exist (i.e. the first time the app is run):

var fileName = "MyAssetBasedFile.txt";
if (!File.Exists(Path.Combine(CacheDir.Path, fileName)))
{
    AssetManager assets = this.Assets;
    using (StreamReader sr = new StreamReader(assets.Open(fileName)))
    using (StreamWriter sw = new StreamWriter(Path.Combine(CacheDir.Path, fileName), append: false))
        sw.Write(sr.ReadToEnd());
}
string content;
using (StreamReader sr = new StreamReader(Path.Combine(CacheDir.Path, fileName)))
{
    content = sr.ReadToEnd();
}
Log.Debug("SO", content);

The next time the app runs you will pick up the one in your cache dir.

来源：https://stackoverflow.com/questions/38824812/how-to-fix-xamarin-forms-system-io-filenotfoundexception-could-not-find-file