> For the complete documentation index, see [llms.txt](https://docs.apryse.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.apryse.com/uwp/search/text-search.md).

# Search for text in a PDF in UWP

Learn how to search for text in a PDF using regular expressions and apply link annotations on highlighted results. Full code sample included. The Apryse uwp SDK streamlines secure document processing.

To search for text in a PDF using regular expression and then apply a link annotation on the highlighted result.

{% hint style="info" %}
In this example, we add a link annotation but any other types of annotations can be applied here such as redaction annotations in the case of a search and redact workflow.
{% endhint %}

{% tabs %}
{% tab title="C#" %}
{% code lineNumbers="true" %}

```csharp
PDFDoc doc = new PDFDoc(filename);
Int32Ref pageNumber = new Int32Ref(0);
StringRef resultString = new StringRef();
StringRef ambientString = new StringRef();
Highlights highlights = new Highlights();
TextSearch textSearch = new TextSearch();

Int32 mode = (Int32)(TextSearchSearchMode.e_whole_word | TextSearchSearchMode.e_page_stop | TextSearchSearchMode.e_highlight);

//use regular expression to find credit card number
mode |= (Int32)(TextSearchSearchMode.e_reg_expression | TextSearchSearchMode.e_highlight);
textSearch.SetMode(mode);
String pattern = "\\d{4}-\\d{4}-\\d{4}-\\d{4}"; //or "(\\d{4}-){3}\\d{4}"
textSearch.SetPattern(pattern);

//call Begin() method to initialize the text search.
textSearch.Begin(doc, pattern, mode, -1, -1);
TextSearchResultCode code = textSearch.Run(pageNumber, resultString, ambientString, highlights);

if (code == TextSearchResultCode.e_found)
{
  //add a link annotation based on the location of the found instance
  hlts.Begin(doc);
  while (hlts.HasNext())
  {
    Page cur_page = doc.GetPage(hlts.GetCurrentPageNumber());
    double[] quads = hlts.GetCurrentQuads();
    int quad_count = quads.Length / 8;
    for (int i = 0; i < quad_count; ++i)
    {
      //assume each quad is an axis-aligned rectangle
      int offset = 8 * i;
      double x1 = Math.Min(Math.Min(Math.Min(quads[offset + 0], quads[offset + 2]), quads[offset + 4]), quads[offset + 6]);
      double x2 = Math.Max(Math.Max(Math.Max(quads[offset + 0], quads[offset + 2]), quads[offset + 4]), quads[offset + 6]);
      double y1 = Math.Min(Math.Min(Math.Min(quads[offset + 1], quads[offset + 3]), quads[offset + 5]), quads[offset + 7]);
      double y2 = Math.Max(Math.Max(Math.Max(quads[offset + 1], quads[offset + 3]), quads[offset + 5]), quads[offset + 7]);

      Annots.Link hyper_link = Annots.Link.Create(doc.GetSDFDoc(), new Rect(x1, y1, x2, y2), Action.CreateURI(doc.GetSDFDoc(), "http://www.apryse.com"));
      hyper_link.RefreshAppearance();
      cur_page.AnnotPushBack(hyper_link);
    }
    hlts.Next();
  }
}
```

{% endcode %}
{% endtab %}
{% endtabs %}

[Search PDF files for text](/uwp/get-started/samples.md#textsearch) Full code sample which shows how to use TextSearch to search text on PDF pages using regular expressions.


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.apryse.com/uwp/search/text-search.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.