Interpolation string from variable c#

Question

I'm trying to interpolate a string combined of two strings in C#. I have following code in VS 2015:

DateTime date = DateTime.Now;
string username = "abc";
string mask = "{date:yy}/{username}";

What I want in result is:

18/abc

I know that I can interpolate it like:

mask = $"{date:yy}/{username}"

but mask is also an input. So i need something like:

string result = $"{mask}"

but the result is :

"{date:yy}/{username}"

Mask is actually downloaded from the database and in each case sequence of information can be different. I need to store in db whole mask and only complement it in code. I can't use String.Replace() method like

mask.Replace({date}, date.ToString())

because I need to have possibility to add some formatting like :yy, :yyyy, :dd etc.

Is there any possibility to do this?

Possible duplicate of [String concatenation: concat() vs "+" operator](https://stackoverflow.com/questions/47605/string-concatenation-concat-vs-operator) — kgzdev, Oct 25 '18 at 11:22
What exactly do you mean by `in each case sequence of information can be different`? Please give us some examples — Rui Jarimba, Oct 25 '18 at 11:31
I think a better way to state your question would be like this: string mask = "{date:yy}/{username}"; .... later .... DateTime date = //something string username = //something string maskWithValues = HowDoIInterpolateThis(mask); — user1529413, Feb 14 '20 at 13:43
https://weblogs.asp.net/bleroy/c-6-string-interpolation-is-not-a-templating-engine-and-it-s-not-the-new-string-format — user1529413, Feb 14 '20 at 13:48

SᴇM · Accepted Answer · 2018-10-25T12:13:54.700

2

You can use string.Format() for that:

string mask = GetMaskFromDB(); //assume it returns "{0}/{1:yy}"
string username = "abc";
DateTime dt = DateTime.Now;

var result = string.Format(mask, username, dt);

Result: "abc/18"

References: DotNetFiddle Example, String.Format Method

edited Oct 25 '18 at 12:13

answered Oct 25 '18 at 11:34

SᴇM

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In one case mask can be "{date}/{username}" but in other the order may change. – Piotr Oct 25 '18 at 11:45
@Piotr In that case your mask will be like `"{1:yy}/{0}";`, so it doesn't matter. – SᴇM Oct 25 '18 at 12:10

score 1 · Answer 2 · answered Oct 25 '18 at 11:22

1

Sure string.Format()

string mask = string.Format("{0:yy}/{1}", date, username);

or string interpolation

string mask = $"{date:yy}/{username}";

answered Oct 25 '18 at 11:22

fubo

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I didn't say precisely. Mask is downloaded from db and I should be generated automatically. – Piotr Oct 25 '18 at 11:28
What I get from db is whole mask, but i can't use it like this: string result = $"{mask}" – Piotr Oct 25 '18 at 11:28

Interpolation string from variable c#

2 Answers2