using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.ComponentModel;

public partial class Default3 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        DataTable dt = new DataTable();
        dt = lstEmployee.ConvertToDataTable();
    }
    public static DataTable ConvertToDataTable<T>(IList<T> list) where T : class
    {
        try
        {
            DataTable table = CreateDataTable<T>();
            Type objType = typeof(T);
            PropertyDescriptorCollection properties = TypeDescriptor.GetProperties(objType);
            foreach (T item in list)
            {
                DataRow row = table.NewRow();
                foreach (PropertyDescriptor property in properties)
                {
                    if (!CanUseType(property.PropertyType)) continue;
                    row[property.Name] = property.GetValue(item) ?? DBNull.Value;
                }

                table.Rows.Add(row);
            }
            return table;
        }
        catch (DataException ex)
        {
            return null;
        }
        catch (Exception ex)
        {
            return null;
        }

    }
    private static DataTable CreateDataTable<T>() where T : class
    {
        Type objType = typeof(T);
        DataTable table = new DataTable(objType.Name);
        PropertyDescriptorCollection properties = TypeDescriptor.GetProperties(objType);
        foreach (PropertyDescriptor property in properties)
        {
            Type propertyType = property.PropertyType;
            if (!CanUseType(propertyType)) continue;

            //nullables must use underlying types
            if (propertyType.IsGenericType && propertyType.GetGenericTypeDefinition() == typeof(Nullable<>))
                propertyType = Nullable.GetUnderlyingType(propertyType);
            //enums also need special treatment
            if (propertyType.IsEnum)
                propertyType = Enum.GetUnderlyingType(propertyType);
            table.Columns.Add(property.Name, propertyType);
        }
        return table;
    }


    private static bool CanUseType(Type propertyType)
    {
        //only strings and value types
        if (propertyType.IsArray) return false;
        if (!propertyType.IsValueType && propertyType != typeof(string)) return false;
        return true;
    }
}

下面是NuGet使用FastMember的2013年更新:

IEnumerable<SomeType> data = ...
DataTable table = new DataTable();
using(var reader = ObjectReader.Create(data)) {
    table.Load(reader);
}

它使用FastMember的元编程API来获得最大的性能。如果你想将它限制到特定的成员(或强制执行顺序)，那么你也可以这样做:

IEnumerable<SomeType> data = ...
DataTable table = new DataTable();
using(var reader = ObjectReader.Create(data, "Id", "Name", "Description")) {
    table.Load(reader);
}

FastMember是Marc Gravell的一个项目。它是金色的，完全是苍蝇!

是的，这个和这个完全相反;反射就足够了——或者如果你需要更快，2.0中的HyperDescriptor，或者3.5中的Expression。实际上，HyperDescriptor应该绰绰有余。

例如:

// remove "this" if not on C# 3.0 / .NET 3.5
public static DataTable ToDataTable<T>(this IList<T> data)
{
    PropertyDescriptorCollection props =
        TypeDescriptor.GetProperties(typeof(T));
    DataTable table = new DataTable();
    for(int i = 0 ; i < props.Count ; i++)
    {
        PropertyDescriptor prop = props[i];
        table.Columns.Add(prop.Name, prop.PropertyType);
    }
    object[] values = new object[props.Count];
    foreach (T item in data)
    {
        for (int i = 0; i < values.Length; i++)
        {
            values[i] = props[i].GetValue(item);
        }
        table.Rows.Add(values);
    }
    return table;        
}

现在，只需一行代码，你就可以让它比反射快很多很多倍(通过为对象类型T启用HyperDescriptor)。

编辑重新性能查询;下面是测试结果:

Vanilla 27179
Hyper   6997

我怀疑瓶颈已经从成员访问转移到数据表性能…我怀疑你在这方面还能提高多少……

代码:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Diagnostics;
public class MyData
{
    public int A { get; set; }
    public string B { get; set; }
    public DateTime C { get; set; }
    public decimal D { get; set; }
    public string E { get; set; }
    public int F { get; set; }
}

static class Program
{
    static void RunTest(List<MyData> data, string caption)
    {
        GC.Collect(GC.MaxGeneration, GCCollectionMode.Forced);
        GC.WaitForPendingFinalizers();
        GC.WaitForFullGCComplete();
        Stopwatch watch = Stopwatch.StartNew();
        for (int i = 0; i < 500; i++)
        {
            data.ToDataTable();
        }
        watch.Stop();
        Console.WriteLine(caption + "\t" + watch.ElapsedMilliseconds);
    }
    static void Main()
    {
        List<MyData> foos = new List<MyData>();
        for (int i = 0 ; i < 5000 ; i++ ){
            foos.Add(new MyData
            { // just gibberish...
                A = i,
                B = i.ToString(),
                C = DateTime.Now.AddSeconds(i),
                D = i,
                E = "hello",
                F = i * 2
            });
        }
        RunTest(foos, "Vanilla");
        Hyper.ComponentModel.HyperTypeDescriptionProvider.Add(
            typeof(MyData));
        RunTest(foos, "Hyper");
        Console.ReadLine(); // return to exit        
    }
}

2019年的答案，如果你正在使用。net Core——使用Nuget ToDataTable库。优点:

性能优于FastMember 还可以创建结构化的SqlParameters作为SQL Server表值参数

免责声明-我是ToDataTable的作者

性能——我扩展了一些Benchmark . net测试，并将它们包含在ToDataTable repo中。结果如下:

创建100,000行数据表:

                           MacOS         Windows
Reflection                 818.5 ms      818.3 ms
FastMember from           1105.5 ms      976.4 ms
 Mark's answer
Improved FastMember        524.6 ms      456.4 ms
ToDataTable                449.0 ms      376.5 ms

Marc回答中建议的FastMember方法的性能似乎比Mary使用反射的回答差，但我使用FastMember TypeAccessor滚动了另一个方法，它的性能要好得多。尽管如此，ToDataTable包的性能还是优于其他包。

我不得不修改Marc Gravell的示例代码来处理可空类型和空值。我在下面附上了一个工作版本。谢谢你马克。

public static DataTable ToDataTable<T>(this IList<T> data)
{
    PropertyDescriptorCollection properties = 
        TypeDescriptor.GetProperties(typeof(T));
    DataTable table = new DataTable();
    foreach (PropertyDescriptor prop in properties)
        table.Columns.Add(prop.Name, Nullable.GetUnderlyingType(prop.PropertyType) ?? prop.PropertyType);
    foreach (T item in data)
    {
        DataRow row = table.NewRow();
        foreach (PropertyDescriptor prop in properties)
             row[prop.Name] = prop.GetValue(item) ?? DBNull.Value;
        table.Rows.Add(row);
    }
    return table;
}

另一种方法是:

  List<WhateEver> lst = getdata();
  string json = Newtonsoft.Json.JsonConvert.SerializeObject(lst);
  DataTable pDt = JsonConvert.DeserializeObject<DataTable>(json);

 Dim counties As New List(Of County)
 Dim dtCounties As DataTable
 dtCounties = _combinedRefRepository.Get_Counties()
 If dtCounties.Rows.Count <> 0 Then
    For Each row As DataRow In dtCounties.Rows
      Dim county As New County
      county.CountyId = row.Item(0).ToString()
      county.CountyName = row.Item(1).ToString().ToUpper()
      counties.Add(county)
    Next
    dtCounties.Dispose()
 End If