我有几个方法返回不同的泛型列表。

在。net中存在任何类静态方法或将任何列表转换为数据表?我唯一能想到的是使用反射来做到这一点。

如果我有这个:

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

(这下代码当然不工作,但我想有这样的可能性:

DataTable dt = (DataTable) whatever;

当前回答

另一种方法是:

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

其他回答

我意识到这里已经关门有一段时间了;然而,我有一个解决这个特定问题的解决方案,但需要稍微扭转:列和数据表需要预先定义/已经实例化。然后我只需将类型插入到数据表中。

下面是我所做的一个例子:

public static class Test
{
    public static void Main()
    {
        var dataTable = new System.Data.DataTable(Guid.NewGuid().ToString());

        var columnCode = new DataColumn("Code");
        var columnLength = new DataColumn("Length");
        var columnProduct = new DataColumn("Product");

        dataTable.Columns.AddRange(new DataColumn[]
            {
                columnCode,
                columnLength,
                columnProduct
            });

        var item = new List<SomeClass>();

        item.Select(data => new
        {
            data.Id,
            data.Name,
            data.SomeValue
        }).AddToDataTable(dataTable);
    }
}

static class Extensions
{
    public static void AddToDataTable<T>(this IEnumerable<T> enumerable, System.Data.DataTable table)
    {
        if (enumerable.FirstOrDefault() == null)
        {
            table.Rows.Add(new[] {string.Empty});
            return;
        }

        var properties = enumerable.FirstOrDefault().GetType().GetProperties();

        foreach (var item in enumerable)
        {
            var row = table.NewRow();
            foreach (var property in properties)
            {
                row[property.Name] = item.GetType().InvokeMember(property.Name, BindingFlags.GetProperty, null, item, null);
            }
            table.Rows.Add(row);
        }
    }
}

这是一个简单的混合溶液。 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;
}

如果你使用VB。NET,那么这个类就会完成这项工作。

Imports System.Reflection
''' <summary>
''' Convert any List(Of T) to a DataTable with correct column types and converts Nullable Type values to DBNull
''' </summary>

Public Class ConvertListToDataset

    Public Function ListToDataset(Of T)(ByVal list As IList(Of T)) As DataTable

        Dim dt As New DataTable()
        '/* Create the DataTable columns */
        For Each pi As PropertyInfo In GetType(T).GetProperties()
            If pi.PropertyType.IsValueType Then
                Debug.Print(pi.Name)
            End If
            If IsNothing(Nullable.GetUnderlyingType(pi.PropertyType)) Then
                dt.Columns.Add(pi.Name, pi.PropertyType)
            Else
                dt.Columns.Add(pi.Name, Nullable.GetUnderlyingType(pi.PropertyType))
            End If
        Next

        '/* Populate the DataTable with the values in the Items in List */
        For Each item As T In list
            Dim dr As DataRow = dt.NewRow()
            For Each pi As PropertyInfo In GetType(T).GetProperties()
                dr(pi.Name) = IIf(IsNothing(pi.GetValue(item)), DBNull.Value, pi.GetValue(item))
            Next
            dt.Rows.Add(dr)
        Next
        Return dt

    End Function

End Class
  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;
    }
}
List<YourModel> data = new List<YourModel>();
DataTable dataTable = Newtonsoft.Json.JsonConvert.DeserializeObject<DataTable>(Newtonsoft.Json.JsonConvert.SerializeObject(data));