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

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.

其他回答

另一种方法是:

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

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;
}
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.

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
 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