Reserved attributes: Determine caller information

Using info attributes, you obtain information about the caller to a method. You obtain the file path of the source code, the line number in the source code, and the member name of the caller. To obtain member caller information, you use attributes that are applied to optional parameters. Each optional parameter specifies a default value. The following table lists the Caller Info attributes that are defined in the System.Runtime.CompilerServices namespace:

Attribute Description Type
CallerFilePathAttribute Full path of the source file that contains the caller. The full path is the path at compile time. String
CallerLineNumberAttribute Line number in the source file from which the method is called. Integer
CallerMemberNameAttribute Method name or property name of the caller. String

This information helps you write tracing, debugging, and create diagnostic tools. The following example shows how to use caller info attributes. On each call to the TraceMessage method, the caller information is substituted as arguments to the optional parameters.

public void DoProcessing()
{
    TraceMessage("Something happened.");
}

public void TraceMessage(string message,
        [CallerMemberName] string memberName = "",
        [CallerFilePath] string sourceFilePath = "",
        [CallerLineNumber] int sourceLineNumber = 0)
{
    Trace.WriteLine("message: " + message);
    Trace.WriteLine("member name: " + memberName);
    Trace.WriteLine("source file path: " + sourceFilePath);
    Trace.WriteLine("source line number: " + sourceLineNumber);
}

// Sample Output:
//  message: Something happened.
//  member name: DoProcessing
//  source file path: c:\Visual Studio Projects\CallerInfoCS\CallerInfoCS\Form1.cs
//  source line number: 31

You specify an explicit default value for each optional parameter. You can't apply caller info attributes to parameters that aren't specified as optional. The caller info attributes don't make a parameter optional. Instead, they affect the default value that's passed in when the argument is omitted. Caller info values are emitted as literals into the Intermediate Language (IL) at compile time. Unlike the results of the StackTrace property for exceptions, the results aren't affected by obfuscation. You can explicitly supply the optional arguments to control the caller information or to hide caller information.

Member names

You can use the CallerMemberName attribute to avoid specifying the member name as a String argument to the called method. By using this technique, you avoid the problem that Rename Refactoring doesn't change the String values. This benefit is especially useful for the following tasks:

  • Using tracing and diagnostic routines.
  • Implementing the INotifyPropertyChanged interface when binding data. This interface allows the property of an object to notify a bound control that the property has changed, so that the control can display the updated information. Without the CallerMemberName attribute, you must specify the property name as a literal.

The following chart shows the member names that are returned when you use the CallerMemberName attribute.

Calls occur within Member name result
Method, property, or event The name of the method, property, or event from which the call originated.
Constructor The string ".ctor"
Static constructor The string ".cctor"
Destructor The string "Finalize"
User-defined operators or conversions The generated name for the member, for example, "op_Addition".
Attribute constructor The name of the method or property to which the attribute is applied. If the attribute is any element within a member (such as a parameter, a return value, or a generic type parameter), this result is the name of the member that's associated with that element.
No containing member (for example, assembly-level or attributes that are applied to types) The default value of the optional parameter.

See also