[c#] 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 outputs the string foo {0}.

Is there a way to escape the brackets?

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>

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}}}";
//Output will be:  foo {1, 2, 3}

or you can use c# string interpolation like this (feature available in C# 6.0)

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

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}""}}";

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

So this

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

will output "foo {1,2,3}".

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 gottach and String Formatting FAQ

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}""}}";

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}}}";
//Output will be:  foo {1, 2, 3}

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);

or you can use c# string interpolation like this (feature available in C# 6.0)

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

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

My objective:

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

Code c#:

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 }}.

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);

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);

[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);
}

[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);
}

My objective:

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

Code c#:

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

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);

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>