> 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/xamarin/guides/features/search/text-search.md).

# Search for text in a PDF in Xamarin

Learn how to search for text in a PDF using regular expressions and apply link annotations on highlighted results. Full code sample included for searching text on PDF pages. The Apryse Xamarin SDK str

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);
Int32 page_num = 0;
String result_str = "", ambient_string = "";
Highlights hlts = new Highlights();
TextSearch txt_search = new TextSearch();
Int32 mode = (Int32)(TextSearch.SearchMode.e_whole_word | TextSearch.SearchMode.e_page_stop | TextSearch.SearchMode.e_highlight);
String pattern = "";

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

//call Begin() method to initialize the text search.
txt_search.Begin( doc, pattern, mode, -1, -1 );
TextSearch.ResultCode code = txt_search.Run(ref page_num, ref result_str, ref ambient_string, hlts );

if ( code == TextSearch.ResultCode.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, new Rect(x1, y1, x2, y2), Action.CreateURI(doc, "http://www.apryse.com"));
      hyper_link.RefreshAppearance();
      cur_page.AnnotPushBack(hyper_link);
    }
    hlts.Next();
  }
}
```

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

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


---

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```
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