尝试做一个.NET简单、高效、避免OOM的Excel工具 MiniExcel

园友好，最近晚辈尝试做一个.NET简单、高效、避免OOM的Excel工具 MiniExcel

主要目前主流框架大多将资料全载入到内存方便操作，但这会导致内存消耗问题，MiniExcel 尝试以 Stream 角度写底层算法逻辑，能让原本1000多MB占用降低到几MB，避免内存不够情况。适合像是低规格 azure app service 或是读取大文件等情境。

特点

• 低内存耗用，避免OOM(out of memoery)、频繁 Full GC 情况
• 支持即时操作每行数据
  
• 兼具搭配 LINQ 延迟查询特性，能办到低消耗、快速分页等复杂查询
• 轻量，不依赖任何套件，DLL小于100KB
• 简便操作的 API 风格

Get Started

• 读 Excel
• 写 Excel
• Excel Column Name/Index/Ignore Attribute
• 范例

Demo

• LINQPad : Download Basic Demo.linq

安装

请查看 from NuGet

更新日志

请查看 Release Notes

TODO

请查看 TODO

性能测试

以 Test1,000,000x10.xlsx 做基准与主流框架做性能测试，总共 1千万笔 "HelloWorld"，文件大小 23 MB

Benchmarks 逻辑可以在 MiniExcel.Benchmarks 查看或是提交 PR，运行指令

dotnet run -p .enchmarksMiniExcel.Benchmarks -c Release -f netcoreapp3.1 -- -f * --join

最后一次运行结果 :

BenchmarkDotNet=v0.12.1, OS=Windows 10.0.19042
Intel Core i7-7700 CPU 3.60GHz (Kaby Lake), 1 CPU, 8 logical and 4 physical cores
  [Host]     : .NET Framework 4.8 (4.8.4341.0), X64 RyuJIT
  Job-ZYYABG : .NET Framework 4.8 (4.8.4341.0), X64 RyuJIT
IterationCount=3  LaunchCount=3  WarmupCount=3  

Method	最大内存耗用	平均时间	Gen 0	Gen 1	Gen 2
'MiniExcel QueryFirst'	0.109 MB	726.4 us	-	-	-
'ExcelDataReader QueryFirst'	15.24 MB	10,664,238.2 us	566000.0000	1000.0000	-
'MiniExcel Query'	17.3 MB	14,179,334.8 us	367000.0000	96000.0000	7000.0000
'ExcelDataReader Query'	17.3 MB	22,565,088.7 us	1210000.0000	2000.0000	-
'Epplus QueryFirst'	1,452 MB	18,198,015.4 us	535000.0000	132000.0000	9000.0000
'Epplus Query'	1,451 MB	23,647,471.1 us	1451000.0000	133000.0000	9000.0000
'OpenXmlSDK Query'	1,412 MB	52,003,270.1 us	978000.0000	353000.0000	11000.0000
'OpenXmlSDK QueryFirst'	1,413 MB	52,348,659.1 us	978000.0000	353000.0000	11000.0000
'ClosedXml QueryFirst'	2,158 MB	66,188,979.6 us	2156000.0000	575000.0000	9000.0000
'ClosedXml Query'	2,184 MB	191,434,126.6 us	2165000.0000	577000.0000	10000.0000

Method	最大内存耗用	平均时间	Gen 0	Gen 1	Gen 2
'MiniExcel Create Xlsx'	15 MB	11,531,819.8 us	1020000.0000	-	-
'Epplus Create Xlsx'	1,204 MB	22,509,717.7 us	1370000.0000	60000.0000	30000.0000
'OpenXmlSdk Create Xlsx'	2,621 MB	42,473,998.9 us	1370000.0000	460000.0000	50000.0000
'ClosedXml Create Xlsx'	7,141 MB	140,939,928.6 us	5520000.0000	1500000.0000	80000.0000

读 Excel

1. Query 查询 Excel 返回强型别 IEnumerable 数据 [Try it]

public class UserAccount
{
    public Guid ID { get; set; }
    public string Name { get; set; }
    public DateTime BoD { get; set; }
    public int Age { get; set; }
    public bool VIP { get; set; }
    public decimal Points { get; set; }
}

var rows = MiniExcel.Query<UserAccount>(path);

// or

using (var stream = File.OpenRead(path))
    var rows = stream.Query<UserAccount>();

2. Query 查询 Excel 返回Dynamic IEnumerable 数据 [Try it]

• Key 系统预设为 A,B,C,D...Z

MiniExcel	1
Github	2

var rows = MiniExcel.Query(path).ToList();

// or 
using (var stream = File.OpenRead(path))
{
    var rows = stream.Query().ToList();
                
    Assert.Equal("MiniExcel", rows[0].A);
    Assert.Equal(1, rows[0].B);
    Assert.Equal("Github", rows[1].A);
    Assert.Equal(2, rows[1].B);
}

3. 查询数据以第一行数据当Key [Try it]

注意 : 同名以右边数据为准

Input Excel :

Column1	Column2
MiniExcel	1
Github	2

var rows = MiniExcel.Query(useHeaderRow:true).ToList();

// or

using (var stream = File.OpenRead(path))
{
    var rows = stream.Query(useHeaderRow:true).ToList();

    Assert.Equal("MiniExcel", rows[0].Column1);
    Assert.Equal(1, rows[0].Column2);
    Assert.Equal("Github", rows[1].Column1);
    Assert.Equal(2, rows[1].Column2);
}

4. Query 查询支援延迟加载(Deferred Execution)，能配合LINQ First/Take/Skip办到低消耗、高效率复杂查询

举例 : 查询第一笔数据

var row = MiniExcel.Query(path).First();
Assert.Equal("HelloWorld", row.A);

// or

using (var stream = File.OpenRead(path))
{
    var row = stream.Query().First();
    Assert.Equal("HelloWorld", row.A);
}

与其他框架效率比较 :

5. 查询指定 Sheet 名称

MiniExcel.Query(path, sheetName: "SheetName");
//or
stream.Query(sheetName: "SheetName");

6. 查询所有 Sheet 名称跟数据

var sheetNames = MiniExcel.GetSheetNames(path).ToList();
foreach (var sheetName in sheetNames)
{
    var rows = MiniExcel.Query(path, sheetName: sheetName);
}

7. 查询所有栏(列)

var columns = MiniExcel.GetColumns(path); // e.g result : ["A","B"...]

var cnt = columns.Count;  // get column count

8. Dynamic Query 转成 IDictionary<string,object> 数据

foreach(IDictionary<string,object> row in MiniExcel.Query(path))
{
    //..
}

写 Excel

1. 必须是非abstract 类别有公开无参数构造函数
2. MiniExcel SaveAs 支援 IEnumerable参数延迟查询，除非必要请不要使用 ToList 等方法读取全部数据到内存

图片 : 是否呼叫 ToList 的内存差别

1. Anonymous or strongly type [Try it]

var path = Path.Combine(Path.GetTempPath(), $"{Guid.NewGuid()}.xlsx");
MiniExcel.SaveAs(path, new[] {
    new { Column1 = "MiniExcel", Column2 = 1 },
    new { Column1 = "Github", Column2 = 2}
});

2. Datatable:

var path = Path.Combine(Path.GetTempPath(), $"{Guid.NewGuid()}.xlsx");
var table = new DataTable();
{
    table.Columns.Add("Column1", typeof(string));
    table.Columns.Add("Column2", typeof(decimal));
    table.Rows.Add("MiniExcel", 1);
    table.Rows.Add("Github", 2);
}

MiniExcel.SaveAs(path, table);

3. Dapper

using (var connection = GetConnection(connectionString))
{
    var rows = connection.Query(@"select 'MiniExcel' as Column1,1 as Column2 union all select 'Github',2");
    MiniExcel.SaveAs(path, rows);
}

4. IEnumerable<IDictionary<string, object>>

var values = new List<Dictionary<string, object>>()
{
    new Dictionary<string,object>{{ "Column1", "MiniExcel" }, { "Column2", 1 } },
    new Dictionary<string,object>{{ "Column1", "Github" }, { "Column2", 2 } }
};
MiniExcel.SaveAs(path, values);

output :

Column1	Column2
MiniExcel	1
Github	2

5. SaveAs 支援 Stream [Try it]

using (var stream = File.Create(path))
{
    stream.SaveAs(values);
}

Excel Column Name/Index/Ignore Attribute

e.g

input excel :

public class ExcelAttributeDemo
{
    [ExcelColumnName("Column1")]
    public string Test1 { get; set; }
    [ExcelColumnName("Column2")]
    public string Test2 { get; set; }
    [ExcelIgnore]
    public string Test3 { get; set; }
    [ExcelColumnIndex("I")] // system will convert "I" to 8 index
    public string Test4 { get; set; } 
    public string Test5 { get; } //wihout set will ignore
    public string Test6 { get; private set; } //un-public set will ignore
    [ExcelColumnIndex(3)] // start with 0
    public string Test7 { get; set; }
}

var rows = MiniExcel.Query<ExcelAttributeDemo>(path).ToList();
Assert.Equal("Column1", rows[0].Test1);
Assert.Equal("Column2", rows[0].Test2);
Assert.Null(rows[0].Test3);
Assert.Equal("Test7", rows[0].Test4);
Assert.Null(rows[0].Test5);
Assert.Null(rows[0].Test6);
Assert.Equal("Test4", rows[0].Test7);

Excel 类别自动判断

MiniExcel 预设会根据扩展名或是 Stream 类别判断是 xlsx 还是 csv，但会有失准时候，请自行指定。

stream.SaveAs(excelType:ExcelType.CSV);
//or
stream.SaveAs(excelType:ExcelType.XLSX);
//or
stream.Query(excelType:ExcelType.CSV);
//or
stream.Query(excelType:ExcelType.XLSX);

范例

1. SQLite & Dapper 读取大数据新增到数据库

note : 请不要呼叫 call ToList/ToArray 等方法，这会将所有数据读到内存内

using (var connection = new SQLiteConnection(connectionString))
{
    connection.Open();
    using (var transaction = connection.BeginTransaction())
    using (var stream = File.OpenRead(path))
    {
       var rows = stream.Query();
       foreach (var row in rows)
             connection.Execute("insert into T (A,B) values (@A,@B)", new { row.A, row.B }, transaction: transaction);
       transaction.Commit();
    }
}

效能:

2. ASP.NET Core 3.1 or MVC 5 下载 Excel Xlsx API Demo Try it

public class ExcelController : Controller
{
    public IActionResult DownloadExcel()
    {
        var values = new[] {
            new { Column1 = "MiniExcel", Column2 = 1 },
            new { Column1 = "Github", Column2 = 2}
        };
        var memoryStream = new MemoryStream();
        memoryStream.SaveAs(values);
        memoryStream.Seek(0, SeekOrigin.Begin);
        return new FileStreamResult(memoryStream, "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet")
        {
            FileDownloadName = "demo.xlsx"
        };
    }

    public IActionResult DownloadExcelFromTmplate()
    {
        var templatePath = "TestTemplateComplex.xlsx";
        var value = new Dictionary<string, object>()
        {
            ["title"] = "FooCompany",
            ["managers"] = new[] {
                new {name="Jack",department="HR"},
                new {name="Loan",department="IT"}
            },
            ["employees"] = new[] {
                new {name="Wade",department="HR"},
                new {name="Felix",department="HR"},
                new {name="Eric",department="IT"},
                new {name="Keaton",department="IT"}
            }
        };
        var memoryStream = new MemoryStream();
        memoryStream.SaveAsByTemplate(templatePath, value);
        memoryStream.Seek(0, SeekOrigin.Begin);
        return new FileStreamResult(memoryStream, "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet")
        {
            FileDownloadName = "demo.xlsx"
        };
    }

    public IActionResult DownloadExcelFromTmplate_StremVersion()
    {
        var templatePath = "TestTemplateComplex.xlsx";
        var tytes = System.IO.File.ReadAllBytes(templatePath);
        var value = new Dictionary<string, object>()
        {
            ["title"] = "FooCompany",
            ["managers"] = new[] {
                new {name="Jack",department="HR"},
                new {name="Loan",department="IT"}
            },
            ["employees"] = new[] {
                new {name="Wade",department="HR"},
                new {name="Felix",department="HR"},
                new {name="Eric",department="IT"},
                new {name="Keaton",department="IT"}
            }
        };
        var memoryStream = new MemoryStream();
        memoryStream.SaveAsByTemplate(tytes, value);
        memoryStream.Seek(0, SeekOrigin.Begin);
        return new FileStreamResult(memoryStream, "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet")
        {
            FileDownloadName = "demo.xlsx"
        };
    }
}

3. 分页查询

void Main()
{
	var rows = MiniExcel.Query(path);
	
	Console.WriteLine("==== No.1 Page ====");
	Console.WriteLine(Page(rows,pageSize:3,page:1));
	Console.WriteLine("==== No.50 Page ====");
	Console.WriteLine(Page(rows,pageSize:3,page:50));
	Console.WriteLine("==== No.5000 Page ====");
	Console.WriteLine(Page(rows,pageSize:3,page:5000));
}

public static IEnumerable<T> Page<T>(IEnumerable<T> en, int pageSize, int page)
{
	return en.Skip(page * pageSize).Take(pageSize);
}

FQA

Q: 如何将查询结果转为 DataTable

提醒 : 不建议使用，因为DataTable会将数据全载入内存，失去MiniExcel低内存消耗功能。

public static DataTable QueryAsDataTable(string path)
{
	var rows = MiniExcel.Query(path, true);
	var dt = new DataTable();
	var first = true;
	foreach (IDictionary<string, object> row in rows)
	{
		if (first)
		{
			foreach (var key in row.Keys)
			{
				var type = row[key]?.GetType() ?? typeof(string);
				dt.Columns.Add(key, type);
			}

			first = false;
		}
		dt.Rows.Add(row.Values.ToArray());
	}
	return dt;
}

局限与警告

• 目前不支援 xls (97-2003) 或是加密文件。