C# Convert interpolated strings into multiple languages

You can use the currently recommended way of localizing in .NET, which is IStringLocalizer.

Here's IStringLocalizer overview, and here's additional info on how to use it with parametrized strings.

In your resource files you can store strings with placeholders in different places, then provide the placeholder values with parameters.

Resources/Program.en.resx

HelloPerson: Hello, {name}!

Resources/Program.pl.resx

HelloPerson: {name}, witaj!

public class LocalizationExample(IStringLocalizer<LocalizationExample> localizer)
{
    public void ShowLocalizedString()
    {
        var text = localizer["HelloPerson", new { Name = "John" }];

        Console.WriteLine(text);
    }
}

You might want to use placeholders in resource Strings instead of directly embedding the variables inside the string, which can later be replaced with values at runtime. For example, in your .resx file, you would write:

English: ShortNameAlreadyExists = "Short Name {0} already exists"

Spanish: ShortNameAlreadyExists = "Nombre corto {0} ya existe"

Then use string.Format to put the variable in the place of string where it goes. Can be in the middle like English or Spanish or in any other place if using German for example.

var localizedString = string.Format(Resources.ShortNameAlreadyExists, header.ShortName);

This can be use for as many variables as you like using {0}, {1} ...

Hope this helps.