How to create an interpolated string from a string? [duplicate]

Question

I'm working on a system that gets templates from a database, then fills in values programmatically:

//using System.Runtime.CompilerServices;

var template = "Hello {0}"; // this string comes from the database
var name = "Joe";
var message = FormattableStringFactory.Create(template, new object[] { name });
Console.WriteLine(message);

This code sample works, but I can only use the numeric notation. I'd like to store the templates in the database in the interpolated string format, like this:

var template = "Hello {name}";

This throws a Run-time exception (line __): Input string was not in a correct format.

Is it possible to create an interpolated string from a string?

String interpolation is just syntax sugar. I am not sure about your needs, but did you think about this scenario ? 1.) know what tokens/ placeholders you have in template; 2.) Pass template, found tokens, data packed in Dictionary<Token, TokenValue> into factory 3.) Iterate over found tokens and replace placeholders template.Replace(tokenItem, tokensData[tokenItem].Value) — Peter M.
– Peter M., Commented May 20, 2019 at 15:17
Both approaches share the same problem for human edits: if it's multiple indexes, then human can screw up with numbers; if it's name, then human may screw up with letter and type it as nmae. I'd keep using old good {0} and will simply split long ones into several simpler, e.g. instead of "Good day {0}, would you like to do {1}" I'd make two sentences. And, well, you can still screw up even with {0}. — Sinatr
– Sinatr, Commented May 20, 2019 at 15:52

Legion · Accepted Answer · 2019-05-20 15:27:59Z

0

I do something similar in a (probably) weird way.... but it works so i try to share with you my conclusion:

public static string ExtendedStringFormat(this string source, List<Tuple<string, string>> values)
    {
        string returnvalue = source;
        foreach(Tuple<string, string> my_touple in values)
        {
            returnvalue = returnvalue.Replace(string.Concat('{', my_touple.Item1, '}'), my_touple.Item2);
        }
        return returnvalue;
    }

And you can call it like below:

            List<Tuple<string, string>> lst =  new List<Tuple<string,string>>();
            lst.Add(new Tuple<string, string>("test","YAYYYYYY"));
            lst.Add(new Tuple<string, string>("test2","YAYYYYYY22222222"));
            string ret = "hem... hi? {test}, {test2}";
            ret = ret.ExtendedStringFormat(lst);

edited May 20, 2019 at 15:27

answered May 20, 2019 at 15:19

Legion

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2 Comments

Joe Maffei Over a year ago

The current implementation uses string.Replace, which is what we're trying to avoid.

Legion Over a year ago

Ok, sorry that my answer not helping you :( Btw what you not like of string.Replace()? Is mutch fast and memory efficient that many alternatives.

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