有没有一种很好的方法将IEnumerable转换为DataTable？
我可以使用反射来获取属性和值，但这似乎有点低效，是否有内置的东西？
（我知道例如：ObtainDataTableFromIEnumerable）
修改：
这个question通知了我处理空值的问题
我在下面编写的代码正确处理空值。
public static DataTable ToDataTable<T>(this IEnumerable<T> items) {
// Create the result table, and gather all properties of a T
DataTable table = new DataTable(typeof(T).Name);
PropertyInfo[] props = typeof(T).GetProperties(BindingFlags.Public | BindingFlags.Instance);
// Add the properties as columns to the datatable
foreach (var prop in props) {
Type propType = prop.PropertyType;
// Is it a nullable type? Get the underlying type
if (propType.IsGenericType && propType.GetGenericTypeDefinition().Equals(typeof(Nullable<>)))
propType = new NullableConverter(propType).UnderlyingType;
table.Columns.Add(prop.Name, propType);
}
// Add the property values per T as rows to the datatable
foreach (var item in items) {
var values = new object[props.Length];
for (var i = 0; i < props.Length; i++)
values[i] = props[i].GetValue(item, null);
table.Rows.Add(values);
}
return table;
}
答案 0 :(得分：92)
看看这个：Convert List/IEnumerable to DataTable/DataView
在我的代码中，我将其更改为扩展方法：
public static DataTable ToDataTable<T>(this List<T> items)
{
var tb = new DataTable(typeof(T).Name);
PropertyInfo[] props = typeof(T).GetProperties(BindingFlags.Public | BindingFlags.Instance);
foreach(var prop in props)
{
tb.Columns.Add(prop.Name, prop.PropertyType);
}
foreach (var item in items)
{
var values = new object[props.Length];
for (var i=0; i<props.Length; i++)
{
values[i] = props[i].GetValue(item, null);
}
tb.Rows.Add(values);
}
return tb;
}
答案 1 :(得分：17)
致所有人：
请注意，接受的答案中有一个与可空类型和DataTable相关的错误。该修复程序可在链接网站（http://www.chinhdo.com/20090402/convert-list-to-datatable/）或我修改后的代码中找到：
///###############################################################
/// <summary>
/// Convert a List to a DataTable.
/// </summary>
/// <remarks>
/// Based on MIT-licensed code presented at http://www.chinhdo.com/20090402/convert-list-to-datatable/ as "ToDataTable"
/// <para/>Code modifications made by Nick Campbell.
/// <para/>Source code provided on this web site (chinhdo.com) is under the MIT license.
/// <para/>Copyright © 2010 Chinh Do
/// <para/>Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
/// <para/>The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
/// <para/>THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
/// <para/>(As per http://www.chinhdo.com/20080825/transactional-file-manager/)
/// </remarks>
/// <typeparam name="T">Type representing the type to convert.</typeparam>
/// <param name="l_oItems">List of requested type representing the values to convert.</param>
/// <returns></returns>
///###############################################################
/// <LastUpdated>February 15, 2010</LastUpdated>
public static DataTable ToDataTable<T>(List<T> l_oItems) {
DataTable oReturn = new DataTable(typeof(T).Name);
object[] a_oValues;
int i;
//#### Collect the a_oProperties for the passed T
PropertyInfo[] a_oProperties = typeof(T).GetProperties(BindingFlags.Public | BindingFlags.Instance);
//#### Traverse each oProperty, .Add'ing each .Name/.BaseType into our oReturn value
//#### NOTE: The call to .BaseType is required as DataTables/DataSets do not support nullable types, so it's non-nullable counterpart Type is required in the .Column definition
foreach(PropertyInfo oProperty in a_oProperties) {
oReturn.Columns.Add(oProperty.Name, BaseType(oProperty.PropertyType));
}
//#### Traverse the l_oItems
foreach (T oItem in l_oItems) {
//#### Collect the a_oValues for this loop
a_oValues = new object[a_oProperties.Length];
//#### Traverse the a_oProperties, populating each a_oValues as we go
for (i = 0; i < a_oProperties.Length; i++) {
a_oValues[i] = a_oProperties[i].GetValue(oItem, null);
}
//#### .Add the .Row that represents the current a_oValues into our oReturn value
oReturn.Rows.Add(a_oValues);
}
//#### Return the above determined oReturn value to the caller
return oReturn;
}
///###############################################################
/// <summary>
/// Returns the underlying/base type of nullable types.
/// </summary>
/// <remarks>
/// Based on MIT-licensed code presented at http://www.chinhdo.com/20090402/convert-list-to-datatable/ as "GetCoreType"
/// <para/>Code modifications made by Nick Campbell.
/// <para/>Source code provided on this web site (chinhdo.com) is under the MIT license.
/// <para/>Copyright © 2010 Chinh Do
/// <para/>Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
/// <para/>The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
/// <para/>THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
/// <para/>(As per http://www.chinhdo.com/20080825/transactional-file-manager/)
/// </remarks>
/// <param name="oType">Type representing the type to query.</param>
/// <returns>Type representing the underlying/base type.</returns>
///###############################################################
/// <LastUpdated>February 15, 2010</LastUpdated>
public static Type BaseType(Type oType) {
//#### If the passed oType is valid, .IsValueType and is logicially nullable, .Get(its)UnderlyingType
if (oType != null && oType.IsValueType &&
oType.IsGenericType && oType.GetGenericTypeDefinition() == typeof(Nullable<>)
) {
return Nullable.GetUnderlyingType(oType);
}
//#### Else the passed oType was null or was not logicially nullable, so simply return the passed oType
else {
return oType;
}
}
请注意，这两个示例都是 NOT 扩展方法，如上例所示。
最后...为我的广泛/过度评论道歉（我有一个肛门/卑鄙的教授，打败了我！;）
答案 2 :(得分：5)
我已经写了一个库来处理这个问题。它叫做DataTableProxy，可以NuGet package的形式使用。代码和文档位于Github
答案 3 :(得分：4)
首先，您需要添加where T:class约束 - 除非GetValue传递，否则您无法在值类型上调用ref。
其次GetValue非常慢并且被调用很多。
为了解决这个问题，我们可以创建一个委托，然后调用它：
MethodInfo method = property.GetGetMethod(true);
Delegate.CreateDelegate(typeof(Func<TClass, TProperty>), method );
问题是我们不知道TProperty，但像往常一样Jon Skeet has the answer - 我们可以使用反射来检索getter委托，但是一旦我们拥有它，我们就不需要了再次反思：
public class ReflectionUtility
{
internal static Func<object, object> GetGetter(PropertyInfo property)
{
// get the get method for the property
MethodInfo method = property.GetGetMethod(true);
// get the generic get-method generator (ReflectionUtility.GetSetterHelper<TTarget, TValue>)
MethodInfo genericHelper = typeof(ReflectionUtility).GetMethod(
"GetGetterHelper",
BindingFlags.Static | BindingFlags.NonPublic);
// reflection call to the generic get-method generator to generate the type arguments
MethodInfo constructedHelper = genericHelper.MakeGenericMethod(
method.DeclaringType,
method.ReturnType);
// now call it. The null argument is because it's a static method.
object ret = constructedHelper.Invoke(null, new object[] { method });
// cast the result to the action delegate and return it
return (Func<object, object>) ret;
}
static Func<object, object> GetGetterHelper<TTarget, TResult>(MethodInfo method)
where TTarget : class // target must be a class as property sets on structs need a ref param
{
// Convert the slow MethodInfo into a fast, strongly typed, open delegate
Func<TTarget, TResult> func = (Func<TTarget, TResult>) Delegate.CreateDelegate(typeof(Func<TTarget, TResult>), method);
// Now create a more weakly typed delegate which will call the strongly typed one
Func<object, object> ret = (object target) => (TResult) func((TTarget) target);
return ret;
}
}
所以现在你的方法变成了：
public static DataTable ToDataTable<T>(this IEnumerable<T> items)
where T: class
{
// ... create table the same way
var propGetters = new List<Func<T, object>>();
foreach (var prop in props)
{
Func<T, object> func = (Func<T, object>) ReflectionUtility.GetGetter(prop);
propGetters.Add(func);
}
// Add the property values per T as rows to the datatable
foreach (var item in items)
{
var values = new object[props.Length];
for (var i = 0; i < props.Length; i++)
{
//values[i] = props[i].GetValue(item, null);
values[i] = propGetters[i](item);
}
table.Rows.Add(values);
}
return table;
}
您可以通过在静态字典中存储每种类型的getter来进一步优化它，然后每种类型只会有一次反射开销。
答案 4 :(得分：0)
没有什么内置的东西，但自己建造它应该很容易。我会按照你的建议做，并使用反射来获取属性并使用它们来创建表的列。然后我将遍历IEnumerable中的每个项目并为每个项目创建一行。唯一需要注意的是，如果您的集合包含多种类型的项目（比如Person和Animal），那么它们可能没有相同的属性。但是如果你需要检查它取决于你的用途。
答案 5 :(得分：0)
我通过向IEnumerable添加扩展方法来解决这个问题。
public static class DataTableEnumerate
{
public static void Fill<T> (this IEnumerable<T> Ts, ref DataTable dt) where T : class
{
//Get Enumerable Type
Type tT = typeof(T);
//Get Collection of NoVirtual properties
var T_props = tT.GetProperties().Where(p => !p.GetGetMethod().IsVirtual).ToArray();
//Fill Schema
foreach (PropertyInfo p in T_props)
dt.Columns.Add(p.Name, p.GetMethod.ReturnParameter.ParameterType.BaseType);
//Fill Data
foreach (T t in Ts)
{
DataRow row = dt.NewRow();
foreach (PropertyInfo p in T_props)
row[p.Name] = p.GetValue(t);
dt.Rows.Add(row);
}
}
}
答案 6 :(得分：0)
我也遇到过这个问题。就我而言，我不知道IEnumerable的类型。所以上面给出的答案不会奏效。但是，我解决了这个问题：
public static DataTable CreateDataTable(IEnumerable source)
{
var table = new DataTable();
int index = 0;
var properties = new List<PropertyInfo>();
foreach (var obj in source)
{
if (index == 0)
{
foreach (var property in obj.GetType().GetProperties())
{
if (Nullable.GetUnderlyingType(property.PropertyType) != null)
{
continue;
}
properties.Add(property);
table.Columns.Add(new DataColumn(property.Name, property.PropertyType));
}
}
object[] values = new object[properties.Count];
for (int i = 0; i < properties.Count; i++)
{
values[i] = properties[i].GetValue(obj);
}
table.Rows.Add(values);
index++;
}
return table;
}
请记住，使用此方法，IEnumerable中至少需要一个项目。如果不是这样，DataTable就不会创建任何列。
答案 7 :(得分：0)
所以，十年后，这仍然是一件事情:)
我已经尝试过此页面上的所有答案（ATOW）
以及一些ILGenerator支持的解决方案（FastMember和Fast.Reflection）。
但是经过编译的Lambda表达式似乎是最快的。
至少在我的用例中（在.Net Core 2.2上）。
这是我现在正在使用的：
public static class EnumerableExtensions {
internal static Func<TClass, object> CompileGetter<TClass>(string propertyName) {
var param = Expression.Parameter(typeof(TClass));
var body = Expression.Convert(Expression.Property(param, propertyName), typeof(object));
return Expression.Lambda<Func<TClass, object>>(body,param).Compile();
}
public static DataTable ToDataTable<T>(this IEnumerable<T> collection) {
var dataTable = new DataTable();
var properties = typeof(T)
.GetProperties(BindingFlags.Public | BindingFlags.Instance)
.Where(p => p.CanRead)
.ToArray();
if (properties.Length < 1) return null;
var getters = new Func<T, object>[properties.Length];
for (var i = 0; i < properties.Length; i++) {
var columnType = Nullable.GetUnderlyingType(properties[i].PropertyType) ?? properties[i].PropertyType;
dataTable.Columns.Add(properties[i].Name, columnType);
getters[i] = CompileGetter<T>(properties[i].Name);
}
foreach (var row in collection) {
var dtRow = new object[properties.Length];
for (var i = 0; i < properties.Length; i++) {
dtRow[i] = getters[i].Invoke(row) ?? DBNull.Value;
}
dataTable.Rows.Add(dtRow);
}
return dataTable;
}
}
仅适用于属性（不适用于字段），但适用于匿名类型。
答案 8 :(得分：0)
如果您使用的是.NET Core，则为2019年的答案-使用Nuget ToDataTable library。优点：
免责声明-我是ToDataTable的作者
性能-我介绍了一些Benchmark .Net测试，并将它们包含在ToDataTable repo中。结果如下：
创建100,000行数据表：
Reflection 818.5 ms
DataTableProxy 1,068.8 ms
ToDataTable 449.0 ms