WeihanLi.Npoi

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Introduction

NPOI extensions based on target framework netstandard2.0.

WeihanLi.Npoi provides a powerful and easy-to-use toolkit for working with Excel and CSV files in .NET applications. It offers:

  • Simple API: Intuitive extension methods for common import/export operations
  • Flexible Configuration: Support for both Attribute-based and FluentAPI configuration
  • High Performance: Optimized for handling large datasets efficiently
  • Rich Features: Advanced capabilities like template export, multi-sheet support, and shadow properties
  • CSV Support: Full support for CSV file operations alongside Excel

Core Features

📥 Data Import

  • Import Excel files to List<TEntity> or IEnumerable<TEntity>
  • Import Excel files to DataTable
  • Import CSV files to entities or DataTable
  • Support for custom header rows and sheet selection
  • Automatic type conversion and data mapping

📤 Data Export

  • Export IEnumerable<TEntity> or DataTable to Excel files (.xls/.xlsx)
  • Export data to Excel byte arrays or streams
  • Export to CSV files or byte arrays
  • Template-based export with placeholders for complex layouts
  • Multi-sheet export in a single workbook

⚙️ Configuration Options

  • Attribute Configuration: Simple decoration with [Column] and [Sheet] attributes
  • FluentAPI Configuration: Powerful and flexible configuration with fluent syntax (Recommended)
  • Custom column mapping, formatting, and transformations
  • Support for shadow properties (columns not in the model)

🎨 Advanced Capabilities

  • InputFormatter/OutputFormatter: Transform data during import/export operations
  • ColumnInputFormatter/ColumnOutputFormatter: Column-specific data transformations
  • CellReader: Custom cell reading logic
  • Template Export: Export data based on pre-designed Excel templates
  • Multi-Sheet Support: Handle multiple sheets in a single workbook
  • Shadow Properties: Define additional export columns not present in your models
  • Auto Column Width: Automatic column width adjustment
  • Freeze Panes: Set freeze panes for better data viewing
  • Filters: Add auto-filters to your Excel sheets

GetStarted

Installation

dotnet add package WeihanLi.Npoi

Quick Start

  1. Export list/dataTable to Excel/csv

    var entities = new List<Entity>();

// Export to Excel file
entities.ToExcelFile(string excelPath);

// Export to Excel bytes
entities.ToExcelBytes(ExcelFormat excelFormat);

// Export to CSV file
entities.ToCsvFile(string csvPath);

// Export to CSV bytes
entities.ToCsvBytes();

  2. Import Excel/csv to List

    // Read Excel first sheet content to List<T>
var entityList = ExcelHelper.ToEntityList<T>(string excelPath);

// Read Excel first sheet content to IEnumerable<T>
var entityList = ExcelHelper.ToEntities<T>(string excelPath);

// Read Excel specific sheet content to List<T>
// You can customize header row index via sheet attribute or fluent api HasSheet
var entityList1 = ExcelHelper.ToEntityList<T>(string excelPath, int sheetIndex);

// Import CSV to List<T>
var entityList2 = CsvHelper.ToEntityList<T>(string csvPath);
var entityList3 = CsvHelper.ToEntityList<T>(byte[] csvBytes);

  3. Import Excel/csv to DataTable

    // Read Excel to DataTable directly, by default read the first sheet content
var dataTable = ExcelHelper.ToDataTable(string excelPath);

// Read Excel workbook's specific sheet to DataTable
var dataTableOfSheetIndex = ExcelHelper.ToDataTable(string excelPath, int sheetIndex);

// Read Excel with custom header row index
var dataTableOfSheetIndex = ExcelHelper.ToDataTable(string excelPath, int sheetIndex, int headerRowIndex);

// Read Excel to DataTable using mapping relations and settings from typeof(T)
var dataTableT = ExcelHelper.ToDataTable<T>(string excelPath);

// Read CSV file data to DataTable
var dataTable1 = CsvHelper.ToDataTable(string csvFilePath);

More Api documentation: https://weihanli.github.io/WeihanLi.Npoi/api/WeihanLi.Npoi.html

Configuration

1. Using Attributes

Add ColumnAttribute on the properties of your entity for export or import operations.

Add SheetAttribute on the entity to configure sheet settings. You can set the StartRowIndex as needed (default is 1).

Example:

[Sheet(SheetName = "TestSheet", SheetIndex = 0, AutoColumnWidthEnabled = true)]
public class TestEntity
{
    [Column("ID", Index = 0)]
    public int PKID { get; set; }

    [Column("Bill Title", Index = 1)]
    public string BillTitle { get; set; }

    [Column("Bill Details", Index = 2)]
    public string BillDetails { get; set; }

    [Column("Created By", Index = 3)]
    public string CreatedBy { get; set; }

    [Column("Created Time", Index = 4, Formatter = "yyyy-MM-dd HH:mm:ss")]
    public DateTime CreatedTime { get; set; }
    
    [Column(IsIgnored = true)]
    public string InternalNote { get; set; }
}

public class TestEntity1
{
    [Column("Username")]
    public string Username { get; set; }

    [Column(IsIgnored = true)]
    public string PasswordHash { get; set; }

    [Column("Amount")]
    public decimal Amount { get; set; } = 1000M;

    [Column("WeChat OpenID")]
    public string WechatOpenId { get; set; }

    [Column("Is Active")]
    public bool IsActive { get; set; }
}

FluentAPI provides greater flexibility and more powerful configuration options.

Example:

var setting = FluentSettings.For<TestEntity>();

// Excel document settings
setting.HasAuthor("WeihanLi")
    .HasTitle("WeihanLi.Npoi test")
    .HasDescription("WeihanLi.Npoi test")
    .HasSubject("WeihanLi.Npoi test");

// Sheet configuration (sheetIndex, sheetName, startRowIndex, autoColumnWidth)
setting.HasSheetConfiguration(0, "SystemSettingsList", 1, true);

// Apply filters and freeze panes
// setting.HasFilter(0, 1).HasFreezePane(0, 1, 2, 1);

// Configure individual properties
setting.Property(_ => _.SettingId)
    .HasColumnIndex(0);

setting.Property(_ => _.SettingName)
    .HasColumnTitle("SettingName")
    .HasColumnIndex(1);

setting.Property(_ => _.DisplayName)
    .HasOutputFormatter((entity, displayName) => $"AAA_{entity.SettingName}_{displayName}")
    .HasInputFormatter((entity, originVal) => originVal.Split(new[] { '_' })[2])
    .HasColumnTitle("DisplayName")
    .HasColumnIndex(2);

setting.Property(_ => _.SettingValue)
    .HasColumnTitle("SettingValue")
    .HasColumnIndex(3);

setting.Property(_ => _.CreatedTime)
    .HasColumnTitle("CreatedTime")
    .HasColumnIndex(4)
    .HasColumnWidth(10)
    .HasColumnFormatter("yyyy-MM-dd HH:mm:ss");

setting.Property(_ => _.CreatedBy)
    .HasColumnInputFormatter(x => x += "_test")
    .HasColumnIndex(5)
    .HasColumnTitle("CreatedBy");

setting.Property(x => x.Enabled)
    .HasColumnInputFormatter(val => "Enabled".Equals(val))
    .HasColumnOutputFormatter(v => v ? "Enabled" : "Disabled");

// Shadow property - define a column that doesn't exist in the model
setting.Property("HiddenProp")
    .HasOutputFormatter((entity, val) => $"HiddenProp_{entity.PKID}");

// Ignore specific properties
setting.Property(_ => _.PKID).Ignored();
setting.Property(_ => _.UpdatedBy).Ignored();
setting.Property(_ => _.UpdatedTime).Ignored();

Advanced Features

Template-based Export

Export data based on pre-designed Excel templates with placeholder support:

entities.ToExcelFileByTemplate(
    templatePath: "path/to/template.xlsx",
    excelPath: "path/to/output.xlsx",
    extraData: new { Author = "WeihanLi", Title = "Export Result" }
);

Learn more: Template Export Documentation

Multi-Sheet Export

Export multiple collections to different sheets in a single workbook:

var workbook = ExcelHelper.PrepareWorkbook(ExcelFormat.Xlsx);
workbook.ImportData(collection1, sheetIndex: 0);
workbook.ImportData(collection2, sheetIndex: 1);
workbook.WriteToFile("multi-sheets.xlsx");

Learn more: Multi-Sheet Documentation

Shadow Properties

Define additional export columns that don't exist in your model:

var settings = FluentSettings.For<TestEntity>();
settings.Property("Employee ID")
    .HasOutputFormatter((entity, val) => $"{entity.UserFields[2].Value}");
settings.Property("Department")
    .HasOutputFormatter((entity, val) => $"{entity.UserFields[1].Value}");

Learn more: Shadow Property Documentation

Documentation

More

see some articles here: https://weihanli.github.io/WeihanLi.Npoi/articles/intro.html

more usage:

Get a workbook 
// load excel workbook from file
var workbook = LoadExcel(string excelPath);

// prepare a workbook accounting to excelPath
var workbook = PrepareWorkbook(string excelPath);

// prepare a workbook accounting to excelPath and custom excel settings
var workbook = PrepareWorkbook(string excelPath, ExcelSetting excelSetting);

// prepare a workbook whether *.xls file
var workbook = PrepareWorkbook(bool isXls);

// prepare a workbook whether *.xls file and custom excel setting
var workbook = PrepareWorkbook(bool isXlsx, ExcelSetting excelSetting);
Rich extensions 
List<TEntity> ToEntityList<TEntity>([NotNull]this IWorkbook workbook)

DataTable ToDataTable([NotNull]this IWorkbook workbook)

ISheet ImportData<TEntity>([NotNull] this ISheet sheet, DataTable dataTable)

int ImportData<TEntity>([NotNull] this IWorkbook workbook, IEnumerable<TEntity> list,
            int sheetIndex)

int ImportData<TEntity>([NotNull] this ISheet sheet, IEnumerable<TEntity> list)

int ImportData<TEntity>([NotNull] this IWorkbook workbook, [NotNull] DataTable dataTable,
            int sheetIndex)

ToExcelFile<TEntity>([NotNull] this IEnumerable<TEntity> entityList,
            [NotNull] string excelPath)

int ToExcelStream<TEntity>([NotNull] this IEnumerable<TEntity> entityList,
            [NotNull] Stream stream)

byte[] ToExcelBytes<TEntity>([NotNull] this IEnumerable<TEntity> entityList)

int ToExcelFile([NotNull] this DataTable dataTable, [NotNull] string excelPath)

int ToExcelStream([NotNull] this DataTable dataTable, [NotNull] Stream stream)

byte[] ToExcelBytes([NotNull] this DataTable dataTable)

byte[] ToExcelBytes([NotNull] this IWorkbook workbook)

int WriteToFile([NotNull] this IWorkbook workbook, string filePath)

object GetCellValue([NotNull] this ICell cell, Type propertyType)

T GetCellValue<T>([NotNull] this ICell cell)

void SetCellValue([NotNull] this ICell cell, object value)

byte[] ToCsvBytes<TEntity>(this IEnumerable<TEntity> entities, bool includeHeader)

ToCsvFile<TEntity>(this IEnumerable<TEntity> entities, string filePath, bool includeHeader)

void ToCsvFile(this DataTable dt, string filePath, bool includeHeader)

byte[] ToCsvBytes(this DataTable dt, bool includeHeader)

Samples

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

  1. Fork the repository
  2. Create your feature branch (git checkout -b feature/AmazingFeature)
  3. Commit your changes (git commit -m 'Add some AmazingFeature')
  4. Push to the branch (git push origin feature/AmazingFeature)
  5. Open a Pull Request

Acknowledgements

  • Thanks to all the contributors and users of this project
  • Thanks to NPOI for the excellent Excel library
  • Thanks to FluentExcel for the FluentAPI inspiration
  • Thanks to JetBrains for the free Rider license

License

This project is licensed under the Apache License 2.0 - see the LICENSE file for details.

Contact & Support

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