How Do Balancing Groups in .NET Regular Expressions Handle Nested Structures?

.NET regular expression in the regular expression: the weapon of handling nested structures

What is a balance group?

In the .NET regular expression engine, the balance group is a powerful feature that allows advanced matching and verification of the nested structure in the string. It can track and operate the capture results from the same group.

The concept of the duplicate group

In the regular expression of the .NET, multiple matches of a single capture group can be captured and visited them after the matching. This is different from other regular expression engines. In other engines, subsequent matching will cover the previous capture. Introduction to the balance group

The balance group (? ...) indicates that if the sub -expression match, the last capture is allowed to pop up from the group stack. If the stack is empty when you try to pop up, the group match fails.

Application: Verify brackets

The balance group is good at verifying whether the parentheses are correctly paired. The following is a mode that matches such string:

Press the left brackets into the stack and pop up the top element of the stack for each right bracket. The non -matching right brackets will fail the pattern matching.

Condition mode

<code>^(?:[^()]|(?<Open>[(])|(?<-Open>[)]))*$</code>

Condition mode, written as (Condition) TruePattern | FalSepattern), helps enhance the function of the balance group. They allow the use conditions (for example, whether the capture stack is non -empty) to determine which mode match. This allows additional verification and error treatment.

The final bracket verification mode

Combined with the balance group and conditional mode, you can create a comprehensive bracket verification mode:

Extension: nested capture and content extraction

The balance group can also be used to capture the nested content. By using (? subpattern), not only the capture is popped from the stack B, but also all the content between the capture and the current group will be pressed into the stack A.

This allows authentication, nested grade capture and content extraction in a regular expression mode.

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