C# String Contains (How it Works for Developers)

IronPDF Overview

Install-Package IronPdf

Basic PDF Text Extraction with IronPDF

IronPDF provides a simple API to extract text from PDF documents. This allows you to easily search for specific content within PDFs.

The following example demonstrates how to extract text from a PDF using IronPDF:

using IronPdf;
using System;

public class Program
{
    public static void Main(string[] args)
    {
        // Load the PDF from a file
        PdfDocument pdf = PdfDocument.FromFile("invoice.pdf");
        // Extract all text from the PDF
        string text = pdf.ExtractAllText();
        // Optionally, print the extracted text to the console
        Console.WriteLine(text);
    }  
}

using IronPdf;
using System;

public class Program
{
    public static void Main(string[] args)
    {
        // Load the PDF from a file
        PdfDocument pdf = PdfDocument.FromFile("invoice.pdf");
        // Extract all text from the PDF
        string text = pdf.ExtractAllText();
        // Optionally, print the extracted text to the console
        Console.WriteLine(text);
    }  
}

In this example, the ExtractAllText() method extracts all the text from the PDF document. This text can then be processed to search for specific keywords or phrases.

Using string.Contains() for Text Search

Once you've extracted the text from the PDF, you can use C#'s built-in string.Contains() method to search for specific words or phrases.

The string.Contains() method returns a Boolean value indicating whether a specified string exists within a string. This is particularly useful for basic text searching.

Here’s how you can use string.Contains() to search for a keyword within the extracted text:

bool isFound = text.Contains("search term", StringComparison.OrdinalIgnoreCase);

bool isFound = text.Contains("search term", StringComparison.OrdinalIgnoreCase);

Practical Example: How to Check if a C# String Contains Keywords in a PDF Document

using IronPdf;
using System;

public class Program
{
    public static void Main(string[] args)
    {
        string searchTerm = "INV-12345";
        // Load the PDF from a file
        PdfDocument pdf = PdfDocument.FromFile("exampleInvoice.pdf");
        // Extract all text from the PDF
        string text = pdf.ExtractAllText();
        // Search for the specific invoice number
        bool isFound = text.Contains(searchTerm, StringComparison.OrdinalIgnoreCase);
        // Provide output based on whether the search term was found
        if (isFound)
        {
            Console.WriteLine($"Invoice number: {searchTerm} found in the document");
        }
        else
        {
            Console.WriteLine($"Invoice number {searchTerm} not found in the document");
        }
    }  
}

using IronPdf;
using System;

public class Program
{
    public static void Main(string[] args)
    {
        string searchTerm = "INV-12345";
        // Load the PDF from a file
        PdfDocument pdf = PdfDocument.FromFile("exampleInvoice.pdf");
        // Extract all text from the PDF
        string text = pdf.ExtractAllText();
        // Search for the specific invoice number
        bool isFound = text.Contains(searchTerm, StringComparison.OrdinalIgnoreCase);
        // Provide output based on whether the search term was found
        if (isFound)
        {
            Console.WriteLine($"Invoice number: {searchTerm} found in the document");
        }
        else
        {
            Console.WriteLine($"Invoice number {searchTerm} not found in the document");
        }
    }  
}

Enhancing Search with Regular Expressions

While string.Contains() works for simple substring searches, you might want to perform more complex searches, such as finding a pattern or a series of keywords. For this, you can use regular expressions.

Here’s an example using a regular expression to search for any valid invoice number format in the PDF text:

using IronPdf;
using System;
using System.Text.RegularExpressions;

public class Program
{
    public static void Main(string[] args)
    {
        // Define a regex pattern for a typical invoice number format (e.g., INV-12345)
        string pattern = @"INV-\d{5}";
        // Load the PDF from a file
        PdfDocument pdf = PdfDocument.FromFile("exampleInvoice.pdf");
        // Extract all text from the PDF
        string text = pdf.ExtractAllText();
        // Perform the regex search
        Match match = Regex.Match(text, pattern);
        // Check if a match was found
        if (match.Success)
        {
            Console.WriteLine($"Invoice number found: {match.Value}");
        }
        else
        {
            Console.WriteLine("No matching invoice number found.");
        }
    }  
}

using IronPdf;
using System;
using System.Text.RegularExpressions;

public class Program
{
    public static void Main(string[] args)
    {
        // Define a regex pattern for a typical invoice number format (e.g., INV-12345)
        string pattern = @"INV-\d{5}";
        // Load the PDF from a file
        PdfDocument pdf = PdfDocument.FromFile("exampleInvoice.pdf");
        // Extract all text from the PDF
        string text = pdf.ExtractAllText();
        // Perform the regex search
        Match match = Regex.Match(text, pattern);
        // Check if a match was found
        if (match.Success)
        {
            Console.WriteLine($"Invoice number found: {match.Value}");
        }
        else
        {
            Console.WriteLine("No matching invoice number found.");
        }
    }  
}

This code will search for any invoice numbers that follow the pattern INV-XXXXX, where XXXXX is a series of digits.

Optimizing Text Extraction

• Handle Large PDFs: If you're dealing with large PDFs, it’s a good idea to extract text in smaller chunks (by page) to reduce memory usage and improve performance.
• Handle Special Encodings: Be mindful of encodings and special characters in the PDF. IronPDF generally handles this well, but complex layouts or fonts may require additional handling.

Integrating IronPDF into .NET Projects

IronPDF integrates easily with .NET projects. After downloading and installing the IronPDF library via NuGet, simply import it into your C# codebase, as shown in the examples above.

IronPDF’s flexibility allows you to build sophisticated document processing workflows, such as:

• Searching for and extracting data from forms.
• Converting HTML to PDF and extracting content.
• Creating reports based on user input or data from databases.