String.Format Method (String, Object)

Replaces one or more format items in a specified string with the string representation of a specified object.

Namespace:  System
Assembly:  mscorlib (in mscorlib.dll)

public static string Format(
	string format,
	Object arg0


Type: System.String

A composite format string.

Type: System.Object

The object to format.

Return Value

Type: System.String
A copy of format in which any format items are replaced by the string representation of arg0.


format is null.


The format item in format is invalid.


The index of a format item is not zero.


For examples and comprehensive usage information about this and other overloads of the Format method, see the Format overload summary.

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

XNA Framework

Supported in: 3.0, 2.0, 1.0

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8
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