来自资源的变量的字符串插值

Question

I'm currently working on a .net 5.0 application.

I need to transform a Resource String with a variable into an exception message.

Expected result: Fruit with Name: 'Apple' does not exist.

Actual result: Fruit with Name: 'error' does not exist.

My Resource string in Translation.resx looks like this:

• Name: MyError
• Value: Fruit with name '{error}' does not exist.

My C# code to parse the message looks like this:

string formatter(string error) => $"{Translation.MyError}";

string message = formatter("Apple");

throw new Exception(message);

Do you know how to solve this issue?

Do you know how to transform a resource string with variable into an interpolated string?

Answer 1

We have the FormattableString class and the FormattableStringFactory .
This is how to use them

string error = "Apple";

// This comes from your resourse.
string myErrorMessage =  "Fruit with name '{0}' does not exist.";
FormattableString s = FormattableStringFactory.Create(myErrorMessage, error);
string message = s.ToString();

However you still need to change your resources files to be as expected by the FormattableStringFactory. You need also to add the System.Runtime.CompilerServices namespace to your project

Answer 2

Another Possibility would be the NugetPackage 'ITVComponents.Formatting'. In the class ITVComponents.Formatting.TextFormat there's an extension-method FormatText, which allows you to do something like this:

var tmp = new {error}.FormatText(Translation.MyError);

where Translation.MyError has the value "Fruit with name '[error]' does not exist."

The object you format can either be

• an object of any type. then public methods/properties/fields can be used
• an IDictionary<string,object>. then all items can be accessed by their name

Under the hood it uses a scripting-engine, so you can also use complex expressions such as

"'[error]' has [error.Length] letters, which is an [error.Length%2==0?\"\":\"un\"]-even number."