C# 将通用列表/枚举转换为数据表？

Convert generic List/Enumerable to DataTable?

提问by Josema

I have few methods that returns different Generic Lists.

我有几个方法可以返回不同的通用列表。

Exists in .net any class static method or whatever to convert any list into a datatable? The only thing that i can imagine is use Reflection to do this.

.net 中是否存在任何类静态方法或将任何列表转换为数据表的任何方法？我唯一能想象的是使用反射来做到这一点。

IF i have this:

如果我有这个：

List<Whatever> whatever = new List<Whatever>();

(This next code doesn't work of course, but i would like to have the possibility of:

（下一个代码当然不起作用，但我希望有以下可能性：

DataTable dt = (DataTable) whatever;

采纳答案by Marc Gravell

Here's a nice 2013 update using FastMemberfrom NuGet:

这是使用来自 NuGet 的FastMember 的2013 年更新：

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

This uses the FastMember's meta-programming API for maximum performance. If you want to restrict it to particular members (or enforce the order), then you can do that too:

这使用 FastMember 的元编程 API 以获得最大性能。如果您想将其限制为特定成员（或强制执行命令），那么您也可以这样做：

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

Editor's Dis/claimer:FastMember is a Marc Gravell project. Its gold and full-on flys!

编辑派息/索赔：FastMember是马克Gravell项目。它的黄金和全飞！

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Yes, this is pretty much the exact opposite of thisone; reflection would suffice - or if you need quicker, HyperDescriptorin 2.0, or maybe Expressionin 3.5. Actually, HyperDescriptorshould be more than adequate.

是的，这几乎是完全相反的这一个; 反射就足够了 - 或者如果你需要更快，HyperDescriptor在 2.0 中，或者Expression在 3.5 中。其实HyperDescriptor应该绰绰有余。

For example:

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;        
}

Now with one line you can make this many many times faster than reflection (by enabling HyperDescriptorfor the object-type T).

现在，通过一行，您可以使其比反射快许多倍（通过启用HyperDescriptorobject-type T）。

---

---

edit re performance query; here's a test rig with results:

编辑重新性能查询；这是一个带有结果的测试台：

Vanilla 27179
Hyper   6997

I suspect that the bottleneck has shifted from member-access to DataTableperformance... I doubt you'll improve much on that...

我怀疑瓶颈已经从成员访问转移到了DataTable性能......我怀疑你会在这方面有所改进......

code:

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        
    }
}

回答by Sadegh

try this

尝试这个

public static DataTable ListToDataTable<T>(IList<T> lst)
{

    currentDT = CreateTable<T>();

    Type entType = typeof(T);

    PropertyDescriptorCollection properties = TypeDescriptor.GetProperties(entType);
    foreach (T item in lst)
    {
        DataRow row = currentDT.NewRow();
        foreach (PropertyDescriptor prop in properties)
        {

            if (prop.PropertyType == typeof(Nullable<decimal>) || prop.PropertyType == typeof(Nullable<int>) || prop.PropertyType == typeof(Nullable<Int64>))
            {
                if (prop.GetValue(item) == null)
                    row[prop.Name] = 0;
                else
                    row[prop.Name] = prop.GetValue(item);
            }
            else
                row[prop.Name] = prop.GetValue(item);                    

        }
        currentDT.Rows.Add(row);
    }

    return currentDT;
}

public static DataTable CreateTable<T>()
{
    Type entType = typeof(T);
    DataTable tbl = new DataTable(DTName);
    PropertyDescriptorCollection properties = TypeDescriptor.GetProperties(entType);
    foreach (PropertyDescriptor prop in properties)
    {
        if (prop.PropertyType == typeof(Nullable<decimal>))
             tbl.Columns.Add(prop.Name, typeof(decimal));
        else if (prop.PropertyType == typeof(Nullable<int>))
            tbl.Columns.Add(prop.Name, typeof(int));
        else if (prop.PropertyType == typeof(Nullable<Int64>))
            tbl.Columns.Add(prop.Name, typeof(Int64));
        else
             tbl.Columns.Add(prop.Name, prop.PropertyType);
    }
    return tbl;
}

回答by Johannes Rudolph

I've written a small library myself to accomplish this task. It uses reflection only for the first time an object type is to be translated to a datatable. It emits a method that will do all the work translating an object type.

我自己编写了一个小型图书馆来完成这项任务。它仅在第一次将对象类型转换为数据表时使用反射。它发出一个方法，该方法将完成翻译对象类型的所有工作。

Its blazing fast. You can find it here: ModelShredder on GoogleCode

它的速度非常快。您可以在这里找到它： GoogleCode 上的 ModelShredder

回答by A.Baudouin

This is a simple mix of the solutions. It work with Nullable types.

这是解决方案的简单组合。它适用于 Nullable 类型。

public static DataTable ToDataTable<T>(this IList<T> list)
{
  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, Nullable.GetUnderlyingType(prop.PropertyType) ?? prop.PropertyType);
  }
  object[] values = new object[props.Count];
  foreach (T item in list)
  {
    for (int i = 0; i < values.Length; i++)
      values[i] = props[i].GetValue(item) ?? DBNull.Value;
    table.Rows.Add(values);
  }
  return table;
}

回答by Mary Hamlin

I had to modify Marc Gravell's sample code to handle nullable types and null values. I have included a working version below. Thanks Marc.

我不得不修改 Marc Gravell 的示例代码来处理可空类型和空值。我在下面包含了一个工作版本。谢谢马克。

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;
}

回答by Mithir

It's also possible through XmlSerialization.
The idea is - serialize to `XML` and then `readXml` method of `DataSet`.

I use this code (from an answer in SO, forgot where)

        public static string SerializeXml<T>(T value) where T : class
    {
        if (value == null)
        {
            return null;
        }

        XmlSerializer serializer = new XmlSerializer(typeof(T));

        XmlWriterSettings settings = new XmlWriterSettings();

        settings.Encoding = new UnicodeEncoding(false, false);
        settings.Indent = false;
        settings.OmitXmlDeclaration = false;
        // no BOM in a .NET string

        using (StringWriter textWriter = new StringWriter())
        {
            using (XmlWriter xmlWriter = XmlWriter.Create(textWriter, settings))
            {
               serializer.Serialize(xmlWriter, value);
            }
            return textWriter.ToString();
        }
    }

so then it's as simple as:

            string xmlString = Utility.SerializeXml(trans.InnerList);

        DataSet ds = new DataSet("New_DataSet");
        using (XmlReader reader = XmlReader.Create(new StringReader(xmlString)))
        { 
            ds.Locale = System.Threading.Thread.CurrentThread.CurrentCulture;
            ds.ReadXml(reader); 
        }

Not sure how it stands against all the other answers to this post, but it's also a possibility.

回答by Jürgen Steinblock

This link on MSDN is worth a visit: How to: Implement CopyToDataTable<T> Where the Generic Type T Is Not a DataRow

MSDN 上的这个链接值得一看：How to: Implement CopyToDataTable<T> Where the Generic Type T Is Not a DataRow

This adds an extension method that lets you do this:

这添加了一个扩展方法，让您可以执行此操作：

// Create a sequence. 
Item[] items = new Item[] 
{ new Book{Id = 1, Price = 13.50, Genre = "Comedy", Author = "Gustavo Achong"}, 
  new Book{Id = 2, Price = 8.50, Genre = "Drama", Author = "Jessie Zeng"},
  new Movie{Id = 1, Price = 22.99, Genre = "Comedy", Director = "Marissa Barnes"},
  new Movie{Id = 1, Price = 13.40, Genre = "Action", Director = "Emmanuel Fernandez"}};

// Query for items with price greater than 9.99.
var query = from i in items
             where i.Price > 9.99
             orderby i.Price
             select i;

// Load the query results into new DataTable.
DataTable table = query.CopyToDataTable();

回答by Craig Gjerdingen

Marc Gravell's answer but in VB.NET

Marc Gravell 的回答但在 VB.NET 中

Public Shared Function ToDataTable(Of T)(data As IList(Of T)) As DataTable
    Dim props As PropertyDescriptorCollection = TypeDescriptor.GetProperties(GetType(T))
    Dim table As New DataTable()
    For i As Integer = 0 To props.Count - 1
            Dim prop As PropertyDescriptor = props(i)
            table.Columns.Add(prop.Name, prop.PropertyType)
    Next
    Dim values As Object() = New Object(props.Count - 1) {}
    For Each item As T In data
            For i As Integer = 0 To values.Length - 1
                    values(i) = props(i).GetValue(item)
            Next
            table.Rows.Add(values)
    Next
    Return table
End Function

回答by Onur Omer

A small change to Marc's answerto make it work with value types like List<string>to data table:

对Marc 的答案进行了一个小改动，使其适用List<string>于数据表等值类型：

public static DataTable ListToDataTable<T>(IList<T> data)
{
    DataTable table = new DataTable();

    //special handling for value types and string
    if (typeof(T).IsValueType || typeof(T).Equals(typeof(string)))
    {

        DataColumn dc = new DataColumn("Value");
        table.Columns.Add(dc);
        foreach (T item in data)
        {
            DataRow dr = table.NewRow();
            dr[0] = item;
            table.Rows.Add(dr);
        }
    }
    else
    {
        PropertyDescriptorCollection properties = TypeDescriptor.GetProperties(typeof(T));
        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)
            {
                try
                {
                    row[prop.Name] = prop.GetValue(item) ?? DBNull.Value;
                }
                catch (Exception ex)
                {
                    row[prop.Name] = DBNull.Value;
                }
            }
            table.Rows.Add(row);
        }
    }
    return table;
}

回答by Michael Brown

I also had to come up with an alternate solution, as none of the options listed here worked in my case. I was using an IEnumerable which returned an IEnumerable and the properties couldn't be enumerated. This did the trick:

我还必须想出一个替代解决方案，因为这里列出的选项都不适用于我的情况。我正在使用一个 IEnumerable，它返回一个 IEnumerable 并且无法枚举属性。这做到了：

// remove "this" if not on C# 3.0 / .NET 3.5
public static DataTable ConvertToDataTable<T>(this IEnumerable<T> data)
{
    List<IDataRecord> list = data.Cast<IDataRecord>().ToList();

    PropertyDescriptorCollection props = null;
    DataTable table = new DataTable();
    if (list != null && list.Count > 0)
    {
        props = TypeDescriptor.GetProperties(list[0]);
        for (int i = 0; i < props.Count; i++)
        {
            PropertyDescriptor prop = props[i];
            table.Columns.Add(prop.Name, Nullable.GetUnderlyingType(prop.PropertyType) ?? prop.PropertyType);
        }
    }
    if (props != null)
    {
        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) ?? DBNull.Value;
            }
            table.Rows.Add(values);
        }
    }
    return table;
}