This method uses the composite formatting feature of the .NET Framework to convert the value of an object to its text representation and embed that representation in the current System.Text.StringBuilder object.

The format parameter consists of zero or more runs of text intermixed with zero or more indexed placeholders, called format items, that correspond to objects 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.

The provider parameter specifies an IFormatProvider implementation that can provide formatting information for the objects in args. provider can be any of the following:

• A System.Globalization.CultureInfo object that provides culture-specific formatting information.

• A System.Globalization.NumberFormatInfo object that provides culture-specific formatting information for numeric values in args.

• A System.Globalization.DateTimeFormatInfo object that provides culture-specific formatting information for date and time values in args.

• A custom IFormatProvider implementation that provides formatting information for one or more of the objects in args. Typically, such an implementation also implements the ICustomFormatter interface. The second example in the next section illustrates an StringBuilder.AppendFormat(IFormatProvider, string, Object[]) method call with a custom IFormatProvider implementation.

If the provider parameter is null, format provider information is obtained from the current culture.

args represents the objects to be formatted. Each format item in format is replaced with the string representation of the corresponding object in args. If the format item includes formatString and the corresponding object in args implements the IFormattable interface, then args[index].Format(formatString, provider) defines the formatting. Otherwise, args[index].ToString(provider) defines the formatting.

using System;
using System.Text;

public class StringBuilderTest {
  public static void Main() {

     string a = "very";
     string b = "very";
     string c = "high";

     StringBuilder sb = new StringBuilder("The high ");
     Console.WriteLine(sb.AppendFormat(null, "temperature today was {0}, {1} {2}.", a, b, c) ); 
  }
}
   

The output is

The high temperature today was very, very high.