In .NET enterprise development, converting Excel files to DataTable objects is a common requirement. DataTable serves as a versatile in-memory data structure for subsequent validation, persistance, and presentation operations.

Install the Free Spire.XLS for .NET library via NuGet Package Manager:

1. Right-click project → Manage NuGet Packages
2. Search for the library and install the latest stable version
3. Or execute in Package Manager Console:

Install-Package FreeSpire.XLS

Note: The free version has data volume limitations suitable for small-scale processing.

Core Implementation: Excel to DataTable

Basic Conversion Process

This code demonstrates the complete conversion workflow from Excel file to DataTable:

using Spire.Xls;
using System;
using System.Data;

namespace ExcelConverter
{
    class DataProcessor
    {
        static void ExecuteConversion()
        {
            string sourceFile = "DataFile.xlsx";

            // Initialize workbook and load Excel file
            Workbook excelBook = new Workbook();
            excelBook.LoadFromFile(sourceFile);

            // Access first worksheet
            Worksheet dataSheet = excelBook.Worksheets[0];

            // Convert worksheet data to DataTable
            // First parameter: cell range containing data
            // Second parameter: use first row as column headers
            DataTable resultTable = dataSheet.ExportDataTable(
                dataSheet.AllocatedRange, 
                true
            );

            // Display conversion results
            Console.WriteLine("=== Excel to DataTable Results ===");
            Console.WriteLine($"Total data rows: {resultTable.Rows.Count}");
            
            Console.Write("Column names: ");
            foreach (DataColumn column in resultTable.Columns)
            {
                Console.Write(column.ColumnName + "\t");
            }
            
            Console.WriteLine("\n=== Data Content ===");
            foreach (DataRow record in resultTable.Rows)
            {
                foreach (object field in record.ItemArray)
                {
                    Console.Write(field + "\t");
                }
                Console.WriteLine();
            }
        }
    }
}

Advanced Conversion Scenarios

ExportDataTable provides overloaded methods for customized conversion requirements:

Scenario 1: Convert Specific Cell Range

// Define specific cell range (rows 2-10, columns A-C)
CellRange selectedCells = dataSheet.Range["A2:C10"];
// Convert without using first row as headers
DataTable resultTable = dataSheet.ExportDataTable(selectedCells, false);

Scenario 2: Convert with Formula Evaluation

// Overload method with formula calculation
// Parameters:
// range: target cell range
// useHeaders: first row as column names
// computeFormulas: evaluate formula results
DataTable resultTable = dataSheet.ExportDataTable(
    dataSheet.AllocatedRange,
    true,
    true
);

The ExportDataTable method efficiently handles Excel to DataTable conversion by encapsulating cell iteration and type mapping logic, replacing manual cell-by-cell processing.