How to escape braces (curly brackets) in a format string in .NET

Yes, to output { in string.Format you have to escape it like this: {{

So the following will output "foo {1,2,3}".

String val = "1,2,3";
String.Format(" foo {{{0}}}", val);

But you have to know about a design bug in C# which is that by going on the above logic you would assume this below code will print {24.00}:

int i = 24;
string str = String.Format("{{{0:N}}}", i); // Gives '{N}' instead of {24.00}

But this prints {N}. This is because the way C# parses escape sequences and format characters. To get the desired value in the above case, you have to use this instead:

String.Format("{0}{1:N}{2}", "{", i, "}") // Evaluates to {24.00}

Reference Articles

• String.Format gotcha
• String Formatting FAQ

For you to output foo {1, 2, 3} you have to do something like:

string t = "1, 2, 3";
string v = String.Format(" foo {{{0}}}", t);

To output a { you use {{ and to output a } you use }}.

Or now, you can also use C# string interpolation like this (a feature available in C# 6.0)

Escaping brackets: String interpolation $(""). It is new feature in C# 6.0.

var inVal = "1, 2, 3";
var outVal = $" foo {{{inVal}}}";
// The output will be:  foo {1, 2, 3}