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Posted 2 Feb 2006


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Replace text using tagged expressions

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3.91 (5 votes)
2 Feb 2006
An article on how to replace text using regular expressions, in the VS.NET IDE.


Visual Studio has a very powerful search and replace feature, which is the "tagged expression". You can search and replace using regular expressions, keeping groups of content intact. This can be useful in stuff like refactoring or simply reformatting code.

The basics

A tagged expression is used to identify a piece of text so it can be used in the replacement. You identify a tagged expression with "{" and "}". You can use as many of those as you want.

If you enter the following in the replace dialog:

Find what:

{ content }

Replace with:


You are replacing the group containing "content" with the same.

The following entry will replace the selection with the same:

Find what:


Replace with:


Just to be clear, a picture of the dialog:

Image 1

So what?

OK, I admit, so far it doesn't look very useful. However, from this starting point, you can use any expression to split up text in parts and reassemble them.

Here's a hopefully more interesting example of what you can do:

Given below is an SQL connection string property value after dragging a data source in the designer:

workstation id=LEBOWSKI;packet size=4096;
   user id=sa;data source=LEBOWSKI;
   persist security info=True;
   initial catalog=TheInternet;password=protected

If I replace:

Find what:


Replace with:

options.Add("\1", "\2");\n

You'll get the following:

options.Add("workstation id", "LEBOWSKI");
options.Add("packet size", "4096");
options.Add("user id", "sa");
options.Add("data source", "LEBOWSKI");
options.Add("persist security info", "True");
options.Add("initial catalog", "TheInternet");
options.Add("password", "protected");

Note: "[^=]" means any character except "=", and "*" means as many as there are.

Final words

This may not be a sample you will use yourself, but I hope to have shown you the power of what you can do. And hopefully you'll start using it yourself.

For an overview of the expression syntax, click on the Help button in the Replace dialog. Thanks for reading!


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Comments and Discussions

Generalhi Pin
Mubi | www.mrmubi.com24-Feb-06 2:01
professionalMubi | www.mrmubi.com24-Feb-06 2:01 
GeneralRe: hi Pin
xyzzer2-Mar-06 23:13
Memberxyzzer2-Mar-06 23:13 
GeneralThanks and Regex comment Pin
larbs15-Feb-06 5:20
Memberlarbs15-Feb-06 5:20 
GeneralRe: Thanks and Regex comment Pin
msmits19-Feb-06 22:47
Membermsmits19-Feb-06 22:47 
GeneralI prefer macros Pin
xyzzer9-Feb-06 0:18
Memberxyzzer9-Feb-06 0:18 
In situations as in that sample and especially when converting a table or list of values into a sequence of assignments, calls, declarations etc - I prefer to use macros. It is easier to record and play a macro that does something, than write a regular expression for the same thing. Sometimes only one of the two options is possible so I value them both highly, as they enable to really streamline code generation. Aside from that - it is not something they teach at those programming courses at the university (at least they did not on mine) - so it looks so pro... :]

In this example, using VS2005 I would record the macro as following...

Piece of initial text
workstation id=LEBOWSKI;packet size=4096;user id=sa;data source=LEBOWSKI;persist security info=True;initial catalog=TheInternet;password=protected

The sequence of actions to record the macro:
0. Put the cursor at the beginning of the text
1. Ctrl+Shift+R (starts recording)
2. Type: options.Add("
3. Open a find window (Ctrl+F) and look for character '='
4. Type: ", "
5. Press: Ctrl+Right Arrow (jumps to the end of the word)
6. Type: ");
7. Press Enter for new line
8. Press Delete to remove the semicolon
9. Ctrl+Shift+R to end recording

Now while holding Ctrl+Shift press P a couple of times and you've got your output text with sequence of function calls.
You can even see the actual VB code (Alt+F11) for the macro and edit it if you want to get something more custom, but that probably does not happen very often - at least I have not used that yet.
The key settings for macros might be different in your environment, so you might need to check them or set them up.

Using a similiar technique I often generate properties in C# - just starting with a list of a few dozen words - you just have to change one word into a property, remembering to start with the caret at the beginning of the first word and ending with the caret at the beginning of the second word and using clipboard to put the word in the source of the property a few times.

That is most useful when you want to read some data from a file - e.g. an XML one. You get a list of tag names in your source code, record and use one macro to generate the properties with the same names as XML element names to store the values and then another macro to retrieve values from the XML file and assign them to these properties.
You can create hundreds of lines of tedious code in a matter of seconds. Real robust.

-- modified at 6:25 Thursday 9th February, 2006
The reason why I prefer macros when possible is that you do not have to remember all the special characters and the syntax used in search and replace strings, which is a problem if you only need them once in a while - especially, that they differ among various editors - they even differ between VS and .NET System.Text.RegularExpressions namespace.

-- modified at 6:38 Thursday 9th February, 2006
The macro code sample below can be used to transform a list of names separated by a new line only into a sequence of properties of a C# class, nicely enclosed in #region outlining tag. Just open the macro editor and replace the code of the RecordingModule with the one below.

Option Strict Off
Option Explicit Off
Imports System
Imports EnvDTE
Imports EnvDTE80
Imports System.Diagnostics

Public Module RecordingModule

Sub TemporaryMacro()
DTE.ActiveDocument.Selection.Text = "#region "
DTE.ActiveDocument.Selection.Text = "#endregion"
DTE.ActiveDocument.Selection.Text = "private string m_"
DTE.ActiveDocument.Selection.Text = ";"
DTE.ActiveDocument.Selection.Text = "public string "
DTE.ActiveDocument.Selection.Text = "{"
DTE.ActiveDocument.Selection.Text = "get"
DTE.ActiveDocument.Selection.Text = "{"
DTE.ActiveDocument.Selection.Text = "return m_"
DTE.ActiveDocument.Selection.Text = ";"
DTE.ActiveDocument.Selection.Text = "}"
DTE.ActiveDocument.Selection.Text = "set"
DTE.ActiveDocument.Selection.Text = "{"
DTE.ActiveDocument.Selection.Text = "m_"
DTE.ActiveDocument.Selection.Text = " = value;"
DTE.ActiveDocument.Selection.Text = "}"
DTE.ActiveDocument.Selection.Text = "}"
End Sub
End Module

-- modified at 6:47 Thursday 9th February, 2006
And I hope that is the last time I have modified this post. Big Grin | :-D
GeneralRe: I prefer macros Pin
msmits9-Feb-06 1:56
Membermsmits9-Feb-06 1:56 

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