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 — kgzdev
– kgzdev, Commented Oct 25, 2018 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
– Rui Jarimba, Commented Oct 25, 2018 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
– user1529413, Commented Feb 14, 2020 at 13:43

SᴇM · Accepted Answer · 2018-10-25 12:13:54Z

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, 2018 at 12:13

answered Oct 25, 2018 at 11:34

SᴇM

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2 Comments

Piotr Over a year ago

In one case mask can be "{date}/{username}" but in other the order may change.

SᴇM Over a year ago

@Piotr In that case your mask will be like "{1:yy}/{0}";, so it doesn't matter.

fubo · Accepted Answer · 2018-10-25 11:22:45Z

1

Sure string.Format()

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

or string interpolation

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

answered Oct 25, 2018 at 11:22

fubo

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2 Comments

Piotr Over a year ago

I didn't say precisely. Mask is downloaded from db and I should be generated automatically.

Piotr Over a year ago

What I get from db is whole mask, but i can't use it like this: string result = $"{mask}"

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