如何使用iTextSharp在C#中讀取PDF文檔：

iText 7 (originally iTextSharp) is a powerful open-source library for working with PDFs in .NET. It provides expansive functions for creating, modifying, encrypting, and extracting content from PDF documents. Many developers rely on it for automating document workflows, generating reports, and handling large-scale PDF processing tasks.

One of iText 7’s biggest strengths is its fine-grained control over PDF structures. It supports annotations, form fields, watermarks, and digital signatures, making it a robust tool for advanced document manipulation. Additionally, it’s well-documented and widely used, with robust community support and numerous third-party resources available.

Installing iText 7

To install iText 7 in a .NET project, you can use the NuGet Package Manager in Visual Studio:

Using the NuGet Package Manager Console:

Install-Package itext7

However, iText 7 comes with challenges. Its complex API requires more code for common tasks like text extraction or merging PDFs and lacks built-in support for HTML-to-PDF conversion, making web-to-document workflows more difficult. Additionally, its AGPL licensing requires businesses to purchase a commercial license to avoid open-source distribution requirements.

For developers seeking a more streamlined, high-level API with modern features, IronPDF presents a compelling alternative.

Installation

To get IronPDF up and running in your C# projects, it's as easy as running the following line in the NuGet Package Manager:

Install-Package IronPdf

Or, alternatively, go to Tools > NuGet Package Manager > Manage NuGet Packages for Solution, and search for IronPDF.

Then, simply click “Install” and IronPDF will be added to your project in no time!

Using IronPDF to Extract Text

using IronPdf;

class Program
{
    static void Main()
    {
        string pdfPath = "sample.pdf";

        // Load the PDF document
        var pdf = new PdfDocument(pdfPath);

        // Extract all text from the loaded PDF document
        string extractedText = pdf.ExtractAllText();

        // Output the extracted text to the console
        Console.WriteLine(extractedText);
    }
}

using IronPdf;

class Program
{
    static void Main()
    {
        string pdfPath = "sample.pdf";

        // Load the PDF document
        var pdf = new PdfDocument(pdfPath);

        // Extract all text from the loaded PDF document
        string extractedText = pdf.ExtractAllText();

        // Output the extracted text to the console
        Console.WriteLine(extractedText);
    }
}

Imports IronPdf

Friend Class Program
	Shared Sub Main()
		Dim pdfPath As String = "sample.pdf"

		' Load the PDF document
		Dim pdf = New PdfDocument(pdfPath)

		' Extract all text from the loaded PDF document
		Dim extractedText As String = pdf.ExtractAllText()

		' Output the extracted text to the console
		Console.WriteLine(extractedText)
	End Sub
End Class

var pdf = new PdfDocument("sample.pdf");

// Access text from the first page
string pageText = pdf.Pages[0].Text;

Console.WriteLine(pageText);

var pdf = new PdfDocument("sample.pdf");

// Access text from the first page
string pageText = pdf.Pages[0].Text;

Console.WriteLine(pageText);

Dim pdf = New PdfDocument("sample.pdf")

' Access text from the first page
Dim pageText As String = pdf.Pages(0).Text

Console.WriteLine(pageText)

var pdf1 = new PdfDocument("file1.pdf");
var pdf2 = new PdfDocument("file2.pdf");

// Merge the PDFs into a single document
var combinedPdf = PdfDocument.Merge(pdf1, pdf2);

combinedPdf.SaveAs("combined_output.pdf");

var pdf1 = new PdfDocument("file1.pdf");
var pdf2 = new PdfDocument("file2.pdf");

// Merge the PDFs into a single document
var combinedPdf = PdfDocument.Merge(pdf1, pdf2);

combinedPdf.SaveAs("combined_output.pdf");

Dim pdf1 = New PdfDocument("file1.pdf")
Dim pdf2 = New PdfDocument("file2.pdf")

' Merge the PDFs into a single document
Dim combinedPdf = PdfDocument.Merge(pdf1, pdf2)

combinedPdf.SaveAs("combined_output.pdf")

var pdf = new PdfDocument("sample.pdf");

// Convert the PDF to an HTML string
string htmlContent = pdf.ToHtmlString();

var pdf = new PdfDocument("sample.pdf");

// Convert the PDF to an HTML string
string htmlContent = pdf.ToHtmlString();

Dim pdf = New PdfDocument("sample.pdf")

' Convert the PDF to an HTML string
Dim htmlContent As String = pdf.ToHtmlString()

Reading PDFs with iText 7

using iText.Kernel.Pdf;
using iText.Kernel.Pdf.Canvas.Parser;

class Program
{
    static void Main()
    {
        string pdfPath = "sample.pdf";
        string extractedText = ExtractTextFromPdf(pdfPath);
        Console.WriteLine(extractedText);
    }

    // Method to extract text from a PDF
    static string ExtractTextFromPdf(string pdfPath)
    {
        // Use PdfReader to load the PDF
        using (PdfReader reader = new PdfReader(pdfPath))
        // Open the PDF document for processing
        using (iText.Kernel.Pdf.PdfDocument pdfDoc = new iText.Kernel.Pdf.PdfDocument(reader))
        {
            string text = "";
            // Iterate through each page and extract text
            for (int i = 1; i <= pdfDoc.GetNumberOfPages(); i++)
            {
                text += PdfTextExtractor.GetTextFromPage(pdfDoc.GetPage(i)) + Environment.NewLine;
            }
            return text;
        }
    }
}

using iText.Kernel.Pdf;
using iText.Kernel.Pdf.Canvas.Parser;

class Program
{
    static void Main()
    {
        string pdfPath = "sample.pdf";
        string extractedText = ExtractTextFromPdf(pdfPath);
        Console.WriteLine(extractedText);
    }

    // Method to extract text from a PDF
    static string ExtractTextFromPdf(string pdfPath)
    {
        // Use PdfReader to load the PDF
        using (PdfReader reader = new PdfReader(pdfPath))
        // Open the PDF document for processing
        using (iText.Kernel.Pdf.PdfDocument pdfDoc = new iText.Kernel.Pdf.PdfDocument(reader))
        {
            string text = "";
            // Iterate through each page and extract text
            for (int i = 1; i <= pdfDoc.GetNumberOfPages(); i++)
            {
                text += PdfTextExtractor.GetTextFromPage(pdfDoc.GetPage(i)) + Environment.NewLine;
            }
            return text;
        }
    }
}

Imports iText.Kernel.Pdf
Imports iText.Kernel.Pdf.Canvas.Parser

Friend Class Program
	Shared Sub Main()
		Dim pdfPath As String = "sample.pdf"
		Dim extractedText As String = ExtractTextFromPdf(pdfPath)
		Console.WriteLine(extractedText)
	End Sub

	' Method to extract text from a PDF
	Private Shared Function ExtractTextFromPdf(ByVal pdfPath As String) As String
		' Use PdfReader to load the PDF
		Using reader As New PdfReader(pdfPath)
		' Open the PDF document for processing
		Using pdfDoc As New iText.Kernel.Pdf.PdfDocument(reader)
			Dim text As String = ""
			' Iterate through each page and extract text
			Dim i As Integer = 1
			Do While i <= pdfDoc.GetNumberOfPages()
				text &= PdfTextExtractor.GetTextFromPage(pdfDoc.GetPage(i)) & Environment.NewLine
				i += 1
			Loop
			Return text
		End Using
		End Using
	End Function
End Class

Comparing iText 7 and IronPDF

While iText 7 requires detailed coding to perform PDF operations, IronPDF streamlines these tasks with straightforward methods. For instance, extracting text from a PDF with iText 7 involves multiple steps and extensive code, whereas IronPDF accomplishes this in just a few lines. Additionally, IronPDF's support for HTML to PDF conversion is more robust, handling complex HTML, CSS, and JavaScript seamlessly.

Key Takeaways

• IronPDF simplifies PDF reading and manipulation tasks with a more intuitive and streamlined API, requiring less code to perform common operations.
• IronPDF's text extraction is easier to implement compared to iTextSharp’s more complex iteration process, saving developers time.
• IronPDF’s perpetual licensing is more business-friendly, offering fewer restrictions compared to iTextSharp’s AGPL license.
• IronPDF has better documentation that’s more accessible for quick troubleshooting, making it ideal for developers who want fast solutions without sifting through excessive resources.

IronPDF offers a suite of powerful features that go beyond just PDF reading. These features make it a robust solution for developers looking to optimize their PDF workflows. Here's how IronPDF can enhance your development process:

1. Text Extraction from PDFs

IronPDF allows for easy extraction of text from PDF files, making it ideal for workflows that involve document analysis, data extraction, or content indexing. With IronPDF, you can quickly pull text from PDFs and use it in your applications without dealing with complex parsing.

2. PDF Creation

IronPDF makes it simple to generate PDFs from scratch, whether you're creating reports, invoices, or other types of documents. The tool also supports HTML to PDF conversion, allowing you to leverage existing web content and generate well-formatted PDFs. This is perfect for scenarios where you need to convert web pages or dynamic HTML content into downloadable PDF files.

3. Advanced PDF Features

Beyond basic text extraction and PDF creation, IronPDF supports advanced features such as filling out PDF forms, adding annotations, and manipulating document content. These capabilities are useful in industries like legal, financial, or education where forms and feedback are a regular part of the workflow.

4. Batch Processing

IronPDF is well-suited for processing large numbers of PDF files. Whether you're extracting information from hundreds of documents or converting multiple HTML files to PDFs, IronPDF can automate these tasks and handle them efficiently, saving both time and effort.

5. Automation and Efficiency

IronPDF simplifies PDF manipulation tasks that are often time-consuming and repetitive. By automating tasks like PDF text extraction, form filling, or batch conversion, developers can focus on more complex aspects of their projects while letting IronPDF handle the heavy lifting.

Technical Support and Community Resources

To ensure developers can make the most of IronPDF, the tool is backed by strong support and community resources:

• Technical Support: IronPDF offers direct support through email and a ticketing system, providing assistance for any implementation or technical challenges.
• Community Resources: The IronPDF website includes extensive documentation, tutorials, and blog posts. Developers can also find solutions and share knowledge via GitHub and Stack Overflow, where the community actively discusses best practices and troubleshooting tips.