• Article

String.Format Method (String, Object, Object, Object)

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Replaces the format items in a specified string with the string representation of three specified objects.

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

Syntax

'Declaration
Public Shared Function Format ( _
    format As String, _
    arg0 As Object, _
    arg1 As Object, _
    arg2 As Object _
) As String

public static string Format(
    string format,
    Object arg0,
    Object arg1,
    Object arg2
)

Parameters

  • format
    Type: System.String
    A composite format string (see Remarks).

Return Value

Type: System.String
A copy of format in which the first, second, and third format items have been replaced by the string representations of arg0, arg1, and arg2.

Exceptions

Exception Condition
ArgumentNullException

format is nulla null reference (Nothing in Visual Basic).
FormatException

format is invalid.

-or-

The index of a format item is less than zero, or greater than two.

Remarks

This method uses the composite formatting feature of the .NET Framework to convert the value of an object to its string representation and embed that representation in a string. The .NET Framework provides extensive formatting support, which is described in greater detail in the following formatting topics.

The format parameter consists of zero or more runs of text intermixed with zero or more indexed placeholders, called format items, that correspond to an object in the parameter list of this method. The formatting process replaces each format item with the string representation of the corresponding object.

The syntax of a format item is as follows:

{index[,length][:formatString]}

Elements in square brackets are optional. The following table describes each element. For more information about the composite formatting feature, including the syntax of a format item, see Composite Formatting.

Element

Description

index

The zero-based position in the parameter list of the object to be formatted. If the object specified by index is nulla null reference (Nothing in Visual Basic), the format item is replaced by String.Empty. If there is no parameter in the index position, a FormatException is thrown.

,length

The minimum number of characters in the string representation of the parameter. If positive, the parameter is right-aligned; if negative, it is left-aligned.

:formatString

A standard or custom format string that is supported by the object to be formatted. Possible values for formatString are the same as the values supported by the object's ToString(format) method. If formatString is not specified and the object to be formatted implements the IFormattable interface, nulla null reference (Nothing in Visual Basic) is passed as the value of the format parameter that is used as the IFormattable.ToString format string.
NoteNote:

For the standard and custom format strings used with date and time values, see Standard Date and Time Format Strings and Custom Date and Time Format Strings. For the standard and custom format strings used with numeric values, see Standard Numeric Format Strings and Custom Numeric Format Strings. For the standard format strings used with enumerations, see Enumeration Format Strings.

The leading and trailing brace characters, '{' and '}', are required. To specify a single literal brace character in format, specify two leading or trailing brace characters; that is, "{{" or "}}".

If the value of format is, "Thank you for your purchase of {0:####} copies of Microsoft®.NET (Core Reference).", and arg0 is an Int16 with the value 123, then the return value will be:

"Thank you for your purchase of 123 copies of Microsoft®.NET (Core Reference)."

If the value of format is, "Brad's dog has {0,-8:G} fleas.", arg0 is an Int16 with the value 42, (and in this example, underscores represent padding spaces) then the return value will be:

"Brad's dog has 42______ fleas."

Examples

The following example uses the Format(String, Object, Object, Object) method to create a string that illustrates the result of a Boolean And operation with two integer values. Note that the format string includes six format items, but the method has only three items in its parameter list, because each item is formatted in two different ways.

Imports System.Windows.Media

Public Module Example
   Public Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      outputBlock.FontFamily = New FontFamily("Courier New")

      Dim formatString As String = "    {0,10} ({0,8:X8})" + vbCrLf + _
                                   "And {1,10} ({1,8:X8})" + vbCrLf + _
                                   "  = {2,10} ({2,8:X8})"
      Dim value1 As Integer = 16932
      Dim value2 As Integer = 15421
      Dim result As String = String.Format(formatString, _
                                           value1, value2, value1 And value2)
      outputBlock.Text &= result & vbCrLf
   End Sub
End Module
' The example displays the following output:
'                16932 (00004224)
'       And      15421 (00003C3D)
'         =         36 (00000024)

using System;
using System.Windows.Media;

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      outputBlock.FontFamily = new FontFamily("Courier New");
      string formatString = "    {0,10} ({0,8:X8})\n" +
                            "And {1,10} ({1,8:X8})\n" +
                            "  = {2,10} ({2,8:X8})";
      int value1 = 16932;
      int value2 = 15421;
      string result = String.Format(formatString,
                                    value1, value2, value1 & value2);
      outputBlock.Text += result + "\n";
   }
}
// The example displays the following output:
//                16932 (00004224)
//       And      15421 (00003C3D)
//         =         36 (00000024)

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.