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

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

其他回答

我自己编写了一个小型库来完成这个任务。它只在将对象类型转换为数据表时第一次使用反射。它发出一个方法,该方法将完成转换对象类型的所有工作。

它燃烧得很快。你可以在这里找到它:

ToDataTable()在MoreLinq上的GitHub 原:ModelShredder在GoogleCode,被合并到MoreLinq,从GoogleCode移动到GitHub

试试这个

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;
}
  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;
    }
}

如果你的类中有属性,这行代码是OK的!!

PropertyDescriptorCollection props =
            TypeDescriptor.GetProperties(typeof(T));

但如果你有所有的公共字段,那么使用这个:

public static DataTable ToDataTable<T>(  IList<T> data)
        {
        FieldInfo[] myFieldInfo;
        Type myType = typeof(T);
        // Get the type and fields of FieldInfoClass.
        myFieldInfo = myType.GetFields(BindingFlags.NonPublic | BindingFlags.Instance
            | BindingFlags.Public);

        DataTable dt = new DataTable();
        for (int i = 0; i < myFieldInfo.Length; i++)
            {
            FieldInfo property = myFieldInfo[i];
            dt.Columns.Add(property.Name, property.FieldType);
            }
        object[] values = new object[myFieldInfo.Length];
        foreach (T item in data)
            {
            for (int i = 0; i < values.Length; i++)
                {
                values[i] = myFieldInfo[i].GetValue(item);
                }
            dt.Rows.Add(values);
            }
        return dt;
        }

原来的答案是从上面,我只是编辑使用字段而不是属性

然后这样使用它

 DataTable dt = new DataTable();
            dt = ToDataTable(myBriefs);
            gridData.DataSource = dt;
            gridData.DataBind();

Marc Gravell的回答,但是用VB。网

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