C# 使用反射从类创建数据表？

Using Reflection to create a DataTable from a Class?

提问by vwdewaal

I've just learned about Generics and I'm wondering whether I can use it to dynamically build datatables from my classes.

我刚刚了解了泛型，我想知道是否可以使用它从我的类中动态构建数据表。

Or I might be missing the point here. Here is my code, what I'm trying to do is create a datatable from my existing class and populate it. However I'm getting stuck in my thought process.

或者我可能在这里错过了重点。这是我的代码，我想要做的是从我现有的类创建一个数据表并填充它。然而，我陷入了我的思考过程。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Reflection;
using System.Data;

namespace Generics
{
    public class Dog
    {
        public string Breed { get; set; }
        public string Name { get; set; }
        public int legs { get; set; }
        public bool tail { get; set; }
    }

    class Program
    {
        public static DataTable CreateDataTable(Type animaltype)
        {
            DataTable return_Datatable = new DataTable();
            foreach (PropertyInfo info in animaltype.GetProperties())
            {
                return_Datatable.Columns.Add(new DataColumn(info.Name, info.PropertyType));
            }
            return return_Datatable;
        }

        static void Main(string[] args)
        {
            Dog Killer = new Dog();
            Killer.Breed = "Maltese Poodle";
            Killer.legs = 3;
            Killer.tail = false;
            Killer.Name = "Killer";

            DataTable dogTable = new DataTable();
            dogTable = CreateDataTable(Dog);
//How do I continue from here?


        }      
    }
}    

Now At the DataTablepoint it errors. Also, being new to reflection and Generics, how will I actually populate the data with the Killer class?

现在DataTable它出错了。另外，作为反射和泛型的新手，我将如何使用 Killer 类实际填充数据？

采纳答案by David Airapetyan

Building up on all the previous answers, here is a version that creates a DataTable from any collection:

建立在所有以前的答案的基础上，这是一个从任何集合创建 DataTable 的版本：

public static DataTable CreateDataTable<T>(IEnumerable<T> list)
{
    Type type = typeof(T);
    var properties = type.GetProperties();      

    DataTable dataTable = new DataTable();
    foreach (PropertyInfo info in properties)
    {
        dataTable.Columns.Add(new DataColumn(info.Name, Nullable.GetUnderlyingType(info.PropertyType) ?? info.PropertyType));
    }

    foreach (T entity in list)
    {
        object[] values = new object[properties.Length];
        for (int i = 0; i < properties.Length; i++)
        {
            values[i] = properties[i].GetValue(entity);
        }

        dataTable.Rows.Add(values);
    }

    return dataTable;
}

回答by Mike Perrenoud

The error can be resolved by changing this:

可以通过更改以下内容来解决错误：

dogTable = CreateDataTable(Dog);

to this:

对此：

dogTable = CreateDataTable(typeof(Dog));

But there are some caveats with what you're trying to do. First, a DataTablecan't store complex types, so if Doghas an instance of Caton it, you won't be able to add that as a column. It's up to you what you want to do in that case, but keep it in mind.

但是，您要尝试执行的操作有一些注意事项。首先， aDataTable不能存储复杂类型，因此如果上面Dog有一个实例Cat，您将无法将其添加为列。在这种情况下，您想做什么取决于您，但请记住这一点。

Second, I would recommend that the only time you use a DataTableis when you're building code that knows nothingabout the data its consuming. There are valid use cases for this (e.g. a user-driven data mining tool). If you already have the data in the Doginstance, just use it.

其次，我建议您使用 a 的唯一时间DataTable是在构建对其消耗的数据一无所知的代码时。这有一些有效的用例（例如用户驱动的数据挖掘工具）。如果您已经在Dog实例中拥有数据，只需使用它。

Another little tidbit, this:

另一个小花絮，这个：

DataTable dogTable = new DataTable();
dogTable = CreateDataTable(Dog);

can be condensed to this:

可以浓缩为：

DataTable dogTable = CreateDataTable(Dog);

回答by vwdewaal

Using the answer provided by @neoistheone I've changed the following sections. Works fine now.

使用@neoistheone 提供的答案，我更改了以下部分。现在工作正常。

DataTable dogTable = new DataTable();
        dogTable = CreateDataTable(typeof(Dog));

        dogTable.Rows.Add(Killer.Breed, Killer.Name,Killer.legs,Killer.tail);

        foreach (DataRow row in dogTable.Rows)
        {
            Console.WriteLine(row.Field<string>("Name") + " " + row.Field<string>("Breed"));
            Console.ReadLine();
        }

回答by Franck

my favorite homemade function. it create and populate all at same time. throw any object.

我最喜欢的自制功能。它同时创建和填充。扔任何物体。

 public static DataTable ObjectToData(object o)
 {
    DataTable dt = new DataTable("OutputData");

    DataRow dr = dt.NewRow();
    dt.Rows.Add(dr);

    o.GetType().GetProperties().ToList().ForEach(f =>
    {
        try
        {
            f.GetValue(o, null);
            dt.Columns.Add(f.Name, f.PropertyType);
            dt.Rows[0][f.Name] = f.GetValue(o, null);
        }
        catch { }
    });
    return dt;
 }

回答by Michael Bross

Here's a VB.Net version that creates a data table from a generic list passed to the function as an object. There is also a helper function (ObjectToDataTable) that creates a data table from an object.

这是一个 VB.Net 版本，它从作为对象传递给函数的通用列表创建数据表。还有一个辅助函数 (ObjectToDataTable) 可以从对象创建数据表。

Imports System.Reflection

导入 System.Reflection

   Public Shared Function ListToDataTable(ByVal _List As Object) As DataTable

    Dim dt As New DataTable

    If _List.Count = 0 Then
        MsgBox("The list cannot be empty. This is a requirement of the ListToDataTable function.")
        Return dt
    End If

    Dim obj As Object = _List(0)
    dt = ObjectToDataTable(obj)
    Dim dr As DataRow = dt.NewRow

    For Each obj In _List

        dr = dt.NewRow

        For Each p as PropertyInfo In obj.GetType.GetProperties

            dr.Item(p.Name) = p.GetValue(obj, p.GetIndexParameters)

        Next

        dt.Rows.Add(dr)

    Next

    Return dt

End Function

Public Shared Function ObjectToDataTable(ByVal o As Object) As DataTable

    Dim dt As New DataTable
    Dim properties As List(Of PropertyInfo) = o.GetType.GetProperties.ToList()

    For Each prop As PropertyInfo In properties

        dt.Columns.Add(prop.Name, prop.PropertyType)

    Next

    dt.TableName = o.GetType.Name

    Return dt

End Function

回答by Krasimir Slaveykov

Here is a little bit modified code, which fixed time zone issue for datatime fields:

这是一些修改后的代码，它修复了数据时间字段的时区问题：

    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++)
            {
                if (props[i].PropertyType == typeof(DateTime))
                {
                    DateTime currDT = (DateTime)props[i].GetValue(item);
                    values[i] = currDT.ToUniversalTime();
                }
                else
                {
                    values[i] = props[i].GetValue(item);
                }
            }
            table.Rows.Add(values);
        }
        return table;
    }

回答by CESAR NICOLINI RIVERO

you can convert the object to xml then load the xml document to a dataset, then extract the first table out of the data set. However i dont see how this be practical as it infers creating streams, datasets & datatables and using converstions to create the xml document.

您可以将对象转换为 xml，然后将 xml 文档加载到数据集，然后从数据集中提取第一个表。但是我不明白这如何实用，因为它推断创建流、数据集和数据表并使用转换来创建 xml 文档。

I guess for proof of concept i can understand why. Here is an example, but somewhat hesitant to use it.

我想对于概念证明，我可以理解为什么。这是一个例子，但对使用它有些犹豫。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Reflection;
using System.Data;
using System.Xml.Serialization;

namespace Generics
{
public class Dog
{
    public string Breed { get; set; }
    public string Name { get; set; }
    public int legs { get; set; }
    public bool tail { get; set; }
}

class Program
{
    public static DataTable CreateDataTable(Object[] arr)
    {
        XmlSerializer serializer = new XmlSerializer(arr.GetType());
        System.IO.StringWriter sw = new System.IO.StringWriter();
        serializer.Serialize(sw, arr);
        System.Data.DataSet ds = new System.Data.DataSet();
        System.Data.DataTable dt = new System.Data.DataTable();
        System.IO.StringReader reader = new System.IO.StringReader(sw.ToString());

        ds.ReadXml(reader);
        return ds.Tables[0];
    }

    static void Main(string[] args)
    {
        Dog Killer = new Dog();
        Killer.Breed = "Maltese Poodle";
        Killer.legs = 3;
        Killer.tail = false;
        Killer.Name = "Killer";

        Dog [] array_dog = new Dog[5];
        Dog [0] = killer;
        Dog [1] = killer;
        Dog [2] = killer;
        Dog [3] = killer;
        Dog [4] = killer;

        DataTable dogTable = new DataTable();
        dogTable = CreateDataTable(array_dog);

        // continue here

        }      
    }
}

look the following example here

在此处查看以下示例

回答by cdiggins

Here is a more compact version of David's answerthat is also an extension function. I've posted the code in a C# project on Github.

这是大卫答案的更紧凑版本，它也是一个扩展功能。我已经在 Github 上的C# 项目中发布了代码。

public static class Extensions
{
    public static DataTable ToDataTable<T>(this IEnumerable<T> self)
    {
        var properties = typeof(T).GetProperties();

        var dataTable = new DataTable();
        foreach (var info in properties)
            dataTable.Columns.Add(info.Name, Nullable.GetUnderlyingType(info.PropertyType) 
               ?? info.PropertyType);

        foreach (var entity in self)
            dataTable.Rows.Add(properties.Select(p => p.GetValue(entity)).ToArray());

        return dataTable;
    }     
}

I have found that this works very well in conjunction with code to write a DataTable to CSV.

我发现这与将DataTable写入CSV 的代码结合使用非常有效。