String.Format Method
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Replaces each format item in a specified string with the text equivalent of a corresponding object's value.
This member is overloaded. For complete information about this member, including syntax, usage, and examples, click a name in the overload list.
Overload List
| Name | Description | |
|---|---|---|
.gif "Public method") .gif "Static member") .gif "Supported by Silverlight for Windows Phone") .gif "Supported by Xbox 360") |
Format(String, Object) | Replaces one or more format items in a specified string with the string representation of a specified object. |
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Format(String, array<Object[]) | Replaces the format item in a specified string with the string representation of a corresponding object in a specified array. |
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Format(IFormatProvider, String, array<Object[]) | Replaces the format item in a specified string with the text equivalent of the value of a corresponding object in a specified array. A specified parameter supplies culture-specific formatting information. |
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Format(String, Object, Object) | Replaces the format item in a specified string with the string representations of two specified objects. |
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Format(String, Object, Object, Object) | Replaces the format items in a specified string with the string representation of three specified objects. |
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Remarks
Each overload of the Format method uses the composite formatting feature to include zero-based indexed placeholders, called format items, in a composite format string. At run time, each format item is replaced with the string representation of the corresponding argument in a parameter list. If the value of the argument is nulla null reference (Nothing in Visual Basic), it is replaced with String.Empty. For example, the following call to the Format method includes a format string with three format items, {0}, {1}, and {2}, and an argument list with three items.
Dim dat As Date = #1/17/2012 9:30AM#
Dim city As String = "Chicago"
Dim temp As Integer = -16
Dim output As String = String.Format("At {0} in {1}, the temperature was {2} degrees.",
dat, city, temp)
outputBlock.Text += output
' The example displays the following output:
' At 1/17/2012 9:30:00 AM in Chicago, the temperature was -16 degrees.
DateTime dat = new DateTime(2012, 1, 17, 9, 30, 0);
string city = "Chicago";
int temp = -16;
string output = String.Format("At {0} in {1}, the temperature was {2} degrees.",
dat, city, temp);
inputBlock.Text += output;
// The example displays the following output:
// At 1/17/2012 9:30:00 AM in Chicago, the temperature was -16 degrees.
A format item has the following syntax:
**{index[,**alignment][ **:**formatString] }
Brackets denote optional elements. The opening and closing brackets are required. A format item has the following elements:
index
The zero-based index of the argument whose string representation is to be included at this position in the string.alignment
A signed integer that indicates the total length of the field into which the argument is inserted and whether it is right-aligned (a positive integer) or left-aligned (a negative integer). If alignment is omitted, the string representation of the corresponding argument is inserted in a field with no leading or trailing spaces.formatString
A format string that specifies the format of the corresponding argument's result string. If formatString is omitted, the corresponding argument's parameterless ToString method is called to produce its string representation. If formatString is present, the argument referenced by the format item must implement the IFormattable interface. Types that support format strings include the following:All integral and floating-point types. (See Standard Numeric Format Strings and Custom Numeric Format Strings.)
DateTime and DateTimeOffset. (See Standard Date and Time Format Strings and Custom Date and Time Format Strings.)
All enumeration types. (See Enumeration Format Strings.)
TimeSpan values. (See Standard TimeSpan Format Strings and Custom TimeSpan Format Strings.)
GUIDs. (See the Guid.ToString(String) method.)
The following example illustrates how to use optional elements in format items to produce formatted output.
Module Example
Public Sub Demo(outputBlock As System.Windows.Controls.TextBlock)
' Create array of 5-tuples with population data for three U.S. cities, 1940-1950.
Dim cities() = _
{ Tuple.Create("Los Angeles", #1/1/1940#, 1504277, #1/1/1950#, 1970358),
Tuple.Create("New York", #1/1/1940#, 7454995, #1/1/1950#, 7891957),
Tuple.Create("Chicago", #1/1/1940#, 3396808, #1/1/1950#, 3620962),
Tuple.Create("Detroit", #1/1/1940#, 1623452, #1/1/1950#, 1849568) }
' Display header
Dim header As String = String.Format("{0,-12}{1,8}{2,12}{1,8}{2,12}{3,14}",
"City", "Year", "Population", "Change (%)")
outputBlock.Text += header + vbCrLf + vbCrLf
Dim output As String
For Each city In cities
output = String.Format("{0,-12}{1,8:yyyy}{2,12:N0}{3,8:yyyy}{4,12:N0}{5,14:P1}",
city.Item1, city.Item2, city.Item3, city.Item4, city.Item5,
(city.Item5 - city.Item3)/city.Item3)
outputBlock.Text += output + vbCrLf
Next
End Sub
End Module
' The example displays the following output:
' City Year Population Year Population Change (%)
'
' Los Angeles 1940 1,504,277 1950 1,970,358 31.0 %
' New York 1940 7,454,995 1950 7,891,957 5.9 %
' Chicago 1940 3,396,808 1950 3,620,962 6.6 %
' Detroit 1940 1,623,452 1950 1,849,568 13.9 %
using System;
public class Example
{
public static void Demo(System.Windows.Controls.TextBlock outputBlock)
{
// Create array of 5-tuples with population data for three U.S. cities, 1940-1950.
Tuple<string, DateTime, int, DateTime, int>[] cities =
{ Tuple.Create("Los Angeles", new DateTime(1940, 1, 1), 1504277,
new DateTime(1950, 1, 1), 1970358),
Tuple.Create("New York", new DateTime(1940, 1, 1), 7454995,
new DateTime(1950, 1, 1), 7891957),
Tuple.Create("Chicago", new DateTime(1940, 1, 1), 3396808,
new DateTime(1950, 1, 1), 3620962),
Tuple.Create("Detroit", new DateTime(1940, 1, 1), 1623452,
new DateTime(1950, 1, 1), 1849568) };
// Display header
string header = String.Format("{0,-12}{1,8}{2,12}{1,8}{2,12}{3,14}\n",
"City", "Year", "Population", "Change (%)");
outputBlock.Text += header + Environment.Newline;
string output;
foreach (var city in cities) {
output = String.Format("{0,-12}{1,8:yyyy}{2,12:N0}{3,8:yyyy}{4,12:N0}{5,14:P1}",
city.Item1, city.Item2, city.Item3, city.Item4, city.Item5,
(city.Item5 - city.Item3)/city.Item3 * 1.0);
outputBlock.Text += output + Environment.Newline;
}
}
}
// The example displays the following output:
// City Year Population Year Population Change (%)
//
// Los Angeles 1940 1,504,277 1950 1,970,358 31.0 %
// New York 1940 7,454,995 1950 7,891,957 5.9 %
// Chicago 1940 3,396,808 1950 3,620,962 6.6 %
// Detroit 1940 1,623,452 1950 1,849,568 13.9 %
See Also