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

How can brackets be escaped in using string.Format?

For example:

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

This example doesn't throw an exception, but it outputs the string foo {0}.

Is there a way to escape the brackets?

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}

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

Almost there! The escape sequence for a brace is {{ or }} so for your example you would use:

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

You can use double open brackets and double closing brackets which will only show one bracket on your page.

Escaping curly brackets AND using string interpolation makes for an interesting challenge. You need to use quadruple brackets to escape the string interpolation parsing and string.format parsing.

Escaping Brackets: String Interpolation $("") and String.Format

string localVar = "dynamic";
string templateString = $@"<h2>{0}</h2><div>this is my {localVar} template using a {{{{custom tag}}}}</div>";
string result = string.Format(templateString, "String Interpolation");

// OUTPUT: <h2>String Interpolation</h2><div>this is my dynamic template using a {custom tag}</div>

I came here in search of how to build JSON strings ad-hoc (without serializing a class/object) in C#. In other words, how to escape braces and quotes while using Interpolated Strings in C# and "verbatim string literals" (double quoted strings with '@' prefix), like...

var json = $@"{{""name"":""{name}""}}";

[TestMethod]
public void BraceEscapingTest()
{
    var result = String.Format("Foo {{0}}", "1,2,3");  //"1,2,3" is not parsed
    Assert.AreEqual("Foo {0}", result);

    result = String.Format("Foo {{{0}}}", "1,2,3");
    Assert.AreEqual("Foo {1,2,3}", result);

    result = String.Format("Foo {0} {{bar}}", "1,2,3");
    Assert.AreEqual("Foo 1,2,3 {bar}", result);

    result = String.Format("{{{0:N}}}", 24); //24 is not parsed, see @Guru Kara answer
    Assert.AreEqual("{N}", result);

    result = String.Format("{0}{1:N}{2}", "{", 24, "}");
    Assert.AreEqual("{24.00}", result);

    result = String.Format("{{{0}}}", 24.ToString("N"));
    Assert.AreEqual("{24.00}", result);
}

Or you can use C# string interpolation like this (feature available in C# 6.0):

var value = "1, 2, 3";
var output = $" foo {{{value}}}";

My objective:

I needed to assign the value "{CR}{LF}" to a string variable delimiter.

C# code:

string delimiter= "{{CR}}{{LF}}";

Note: To escape special characters normally you have to use \. For opening curly bracket {, use one extra, like {{. For closing curly bracket }, use one extra, }}.

You can also use like this. var outVal = $" foo {"{"}{inVal}{"}"} --- {"{"}Also Like This{"}"}"

Escaping Brackets: String Interpolation $(""):

Now, you can also use C# string interpolation like this (feature available in C# 6.0):

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