从类型列表获得一个IDataReader的 [英] Get an IDataReader from a typed List
本文介绍了从类型列表获得一个IDataReader的的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我有一个列表与LT;为MyObject＆GT; 一百万的元素。 （它实际上是一个亚音速集合，但它不会从数据库加载）。
I have a List<MyObject> with a million elements. (It is actually a SubSonic Collection but it is not loaded from the database).
使用SqlBulkCopy 如下：
private string FastInsertCollection(string tableName, DataTable tableData)
{
string sqlConn = ConfigurationManager.ConnectionStrings[SubSonicConfig.DefaultDataProvider.ConnectionStringName].ConnectionString;
using (SqlBulkCopy s = new SqlBulkCopy(sqlConn, SqlBulkCopyOptions.TableLock))
{
s.DestinationTableName = tableName;
s.BatchSize = 5000;
s.WriteToServer(tableData);
s.BulkCopyTimeout = SprocTimeout;
s.Close();
}
return sqlConn;
}
我用亚音速的MyObjectCollection.ToDataTable（）从我的收藏建立数据表。然而，这种复制内存中的对象和效率低下。我想用一个使用IDataReader的而不是DataTable的SqlBulkCopy.WriteToServer方法，这样我不重复我的收藏在内存中。
I use SubSonic's MyObjectCollection.ToDataTable() to build the DataTable from my collection. However, this duplicates objects in memory and is inefficient. I'd like to use the SqlBulkCopy.WriteToServer method that uses an IDataReader instead of a DataTable so that I don't duplicate my collection in memory.
什么是从我的列表中IDataReader的最简单的方法？我想我可以实现自定义数据读取器（如这里的http://blogs.microsoft.co.il/blogs/aviwortzel/archive/2008/05/06/implementing-sqlbulkcopy-in-linq-to-sql.aspx) ，但必须有简单的东西不用写了一堆普通code的我能做到的。
What's the easiest way to get an IDataReader from my list? I suppose I could implement a custom data reader (like here http://blogs.microsoft.co.il/blogs/aviwortzel/archive/2008/05/06/implementing-sqlbulkcopy-in-linq-to-sql.aspx) , but there must be something simpler I can do without writing a bunch of generic code.
编辑：
它不会出现一个可以很容易地生成对象的集合的IDataReader的。
接受即使我希望建成框架的东西电流的答案。
It does not appear that one can easily generate an IDataReader from a collection of objects. Accepting current answer even though I was hoping for something built into the framework.
推荐答案
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Get the latest version from the code on this post
没有像在众目睽睽code流失：这里是pretty完整实现。您可以在实例化的IEnumerable的IList，IEnumerable的（ERGO IQueryable的）一个IDataReader的。没有任何令人信服的理由，露出读者泛型类型参数和省略的话，我可以让IEnumerable的＆LT;'一>（匿名类型）。见测试。
Nothing like code churn in plain sight: Here is a pretty complete implementation. You can instantiate an IDataReader over IList IEnumerable, IEnumerable (ergo IQueryable). There is no compelling reason to expose a generic type parameter on the reader and by omitting it, I can allow IEnumerable<'a> (anonymous types). See tests.
源，少xmldocs，很短，在这里与一对夫妇测试包括。源，与xmldocs的休息，测试是 这里 Salient.Data下。
The source, less xmldocs, is short enough to include here with a couple tests. The rest of the source, with xmldocs, and tests is here under Salient.Data.
using System;
using System.Linq;
using NUnit.Framework;
namespace Salient.Data.Tests
{
[TestFixture]
public class EnumerableDataReaderEFFixture
{
[Test]
public void TestEnumerableDataReaderWithIQueryableOfAnonymousType()
{
var ctx = new NorthwindEntities();
var q =
ctx.Orders.Where(o => o.Customers.CustomerID == "VINET").Select(
o =>
new
{
o.OrderID,
o.OrderDate,
o.Customers.CustomerID,
Total =
o.Order_Details.Sum(
od => od.Quantity*((float) od.UnitPrice - ((float) od.UnitPrice*od.Discount)))
});
var r = new EnumerableDataReader(q);
while (r.Read())
{
var values = new object[4];
r.GetValues(values);
Console.WriteLine("{0} {1} {2} {3}", values);
}
}
}
}
using System;
using System.Collections;
using System.Collections.Generic;
using System.Data;
using NUnit.Framework;
namespace Salient.Data.Tests
{
public class DataObj
{
public string Name { get; set; }
public int Age { get; set; }
}
[TestFixture]
public class EnumerableDataReaderFixture
{
private static IEnumerable<DataObj> DataSource
{
get
{
return new List<DataObj>
{
new DataObj {Name = "1", Age = 16},
new DataObj {Name = "2", Age = 26},
new DataObj {Name = "3", Age = 36},
new DataObj {Name = "4", Age = 46}
};
}
}
[Test]
public void TestIEnumerableCtor()
{
var r = new EnumerableDataReader(DataSource, typeof(DataObj));
while (r.Read())
{
var values = new object[2];
int count = r.GetValues(values);
Assert.AreEqual(2, count);
values = new object[1];
count = r.GetValues(values);
Assert.AreEqual(1, count);
values = new object[3];
count = r.GetValues(values);
Assert.AreEqual(2, count);
Assert.IsInstanceOf(typeof(string), r.GetValue(0));
Assert.IsInstanceOf(typeof(int), r.GetValue(1));
Console.WriteLine("Name: {0}, Age: {1}", r.GetValue(0), r.GetValue(1));
}
}
[Test]
public void TestIEnumerableOfAnonymousType()
{
// create generic list
Func<Type, IList> toGenericList =
type => (IList)Activator.CreateInstance(typeof(List<>).MakeGenericType(new[] { type }));
// create generic list of anonymous type
IList listOfAnonymousType = toGenericList(new { Name = "1", Age = 16 }.GetType());
listOfAnonymousType.Add(new { Name = "1", Age = 16 });
listOfAnonymousType.Add(new { Name = "2", Age = 26 });
listOfAnonymousType.Add(new { Name = "3", Age = 36 });
listOfAnonymousType.Add(new { Name = "4", Age = 46 });
var r = new EnumerableDataReader(listOfAnonymousType);
while (r.Read())
{
var values = new object[2];
int count = r.GetValues(values);
Assert.AreEqual(2, count);
values = new object[1];
count = r.GetValues(values);
Assert.AreEqual(1, count);
values = new object[3];
count = r.GetValues(values);
Assert.AreEqual(2, count);
Assert.IsInstanceOf(typeof(string), r.GetValue(0));
Assert.IsInstanceOf(typeof(int), r.GetValue(1));
Console.WriteLine("Name: {0}, Age: {1}", r.GetValue(0), r.GetValue(1));
}
}
[Test]
public void TestIEnumerableOfTCtor()
{
var r = new EnumerableDataReader(DataSource);
while (r.Read())
{
var values = new object[2];
int count = r.GetValues(values);
Assert.AreEqual(2, count);
values = new object[1];
count = r.GetValues(values);
Assert.AreEqual(1, count);
values = new object[3];
count = r.GetValues(values);
Assert.AreEqual(2, count);
Assert.IsInstanceOf(typeof(string), r.GetValue(0));
Assert.IsInstanceOf(typeof(int), r.GetValue(1));
Console.WriteLine("Name: {0}, Age: {1}", r.GetValue(0), r.GetValue(1));
}
}
// remaining tests omitted for brevity
}
}
/*!
* Project: Salient.Data
* File : EnumerableDataReader.cs
* http://spikes.codeplex.com
*
* Copyright 2010, Sky Sanders
* Dual licensed under the MIT or GPL Version 2 licenses.
* See LICENSE.TXT
* Date: Sat Mar 28 2010
*/
using System;
using System.Collections;
using System.Collections.Generic;
namespace Salient.Data
{
/// <summary>
/// Creates an IDataReader over an instance of IEnumerable<> or IEnumerable.
/// Anonymous type arguments are acceptable.
/// </summary>
public class EnumerableDataReader : ObjectDataReader
{
private readonly IEnumerator _enumerator;
private readonly Type _type;
private object _current;
/// <summary>
/// Create an IDataReader over an instance of IEnumerable<>.
///
/// Note: anonymous type arguments are acceptable.
///
/// Use other constructor for IEnumerable.
/// </summary>
/// <param name="collection">IEnumerable<>. For IEnumerable use other constructor and specify type.</param>
public EnumerableDataReader(IEnumerable collection)
{
// THANKS DANIEL!
foreach (Type intface in collection.GetType().GetInterfaces())
{
if (intface.IsGenericType && intface.GetGenericTypeDefinition() == typeof (IEnumerable<>))
{
_type = intface.GetGenericArguments()[0];
}
}
if (_type ==null && collection.GetType().IsGenericType)
{
_type = collection.GetType().GetGenericArguments()[0];
}
if (_type == null )
{
throw new ArgumentException(
"collection must be IEnumerable<>. Use other constructor for IEnumerable and specify type");
}
SetFields(_type);
_enumerator = collection.GetEnumerator();
}
/// <summary>
/// Create an IDataReader over an instance of IEnumerable.
/// Use other constructor for IEnumerable<>
/// </summary>
/// <param name="collection"></param>
/// <param name="elementType"></param>
public EnumerableDataReader(IEnumerable collection, Type elementType)
: base(elementType)
{
_type = elementType;
_enumerator = collection.GetEnumerator();
}
/// <summary>
/// Helper method to create generic lists from anonymous type
/// </summary>
/// <param name="type"></param>
/// <returns></returns>
public static IList ToGenericList(Type type)
{
return (IList) Activator.CreateInstance(typeof (List<>).MakeGenericType(new[] {type}));
}
/// <summary>
/// Return the value of the specified field.
/// </summary>
/// <returns>
/// The <see cref="T:System.Object"/> which will contain the field value upon return.
/// </returns>
/// <param name="i">The index of the field to find.
/// </param><exception cref="T:System.IndexOutOfRangeException">The index passed was outside the range of 0 through <see cref="P:System.Data.IDataRecord.FieldCount"/>.
/// </exception><filterpriority>2</filterpriority>
public override object GetValue(int i)
{
if (i < 0 || i >= Fields.Count)
{
throw new IndexOutOfRangeException();
}
return Fields[i].Getter(_current);
}
/// <summary>
/// Advances the <see cref="T:System.Data.IDataReader"/> to the next record.
/// </summary>
/// <returns>
/// true if there are more rows; otherwise, false.
/// </returns>
/// <filterpriority>2</filterpriority>
public override bool Read()
{
bool returnValue = _enumerator.MoveNext();
_current = returnValue ? _enumerator.Current : _type.IsValueType ? Activator.CreateInstance(_type) : null;
return returnValue;
}
}
}
// <copyright project="Salient.Data" file="ObjectDataReader.cs" company="Sky Sanders">
// This source is a Public Domain Dedication.
// Please see http://spikes.codeplex.com/ for details.
// Attribution is appreciated
// </copyright>
// <version>1.0</version>
using System;
using System.Collections.Generic;
using System.Data;
using Salient.Reflection;
namespace Salient.Data
{
public abstract class ObjectDataReader : IDataReader
{
protected bool Closed;
protected IList<DynamicProperties.Property> Fields;
protected ObjectDataReader()
{
}
protected ObjectDataReader(Type elementType)
{
SetFields(elementType);
Closed = false;
}
#region IDataReader Members
public abstract object GetValue(int i);
public abstract bool Read();
#endregion
#region Implementation of IDataRecord
public int FieldCount
{
get { return Fields.Count; }
}
public virtual int GetOrdinal(string name)
{
for (int i = 0; i < Fields.Count; i++)
{
if (Fields[i].Info.Name == name)
{
return i;
}
}
throw new IndexOutOfRangeException("name");
}
object IDataRecord.this[int i]
{
get { return GetValue(i); }
}
public virtual bool GetBoolean(int i)
{
return (Boolean) GetValue(i);
}
public virtual byte GetByte(int i)
{
return (Byte) GetValue(i);
}
public virtual char GetChar(int i)
{
return (Char) GetValue(i);
}
public virtual DateTime GetDateTime(int i)
{
return (DateTime) GetValue(i);
}
public virtual decimal GetDecimal(int i)
{
return (Decimal) GetValue(i);
}
public virtual double GetDouble(int i)
{
return (Double) GetValue(i);
}
public virtual Type GetFieldType(int i)
{
return Fields[i].Info.PropertyType;
}
public virtual float GetFloat(int i)
{
return (float) GetValue(i);
}
public virtual Guid GetGuid(int i)
{
return (Guid) GetValue(i);
}
public virtual short GetInt16(int i)
{
return (Int16) GetValue(i);
}
public virtual int GetInt32(int i)
{
return (Int32) GetValue(i);
}
public virtual long GetInt64(int i)
{
return (Int64) GetValue(i);
}
public virtual string GetString(int i)
{
return (string) GetValue(i);
}
public virtual bool IsDBNull(int i)
{
return GetValue(i) == null;
}
object IDataRecord.this[string name]
{
get { return GetValue(GetOrdinal(name)); }
}
public virtual string GetDataTypeName(int i)
{
return GetFieldType(i).Name;
}
public virtual string GetName(int i)
{
if (i < 0 || i >= Fields.Count)
{
throw new IndexOutOfRangeException("name");
}
return Fields[i].Info.Name;
}
public virtual int GetValues(object[] values)
{
int i = 0;
for (; i < Fields.Count; i++)
{
if (values.Length <= i)
{
return i;
}
values[i] = GetValue(i);
}
return i;
}
public virtual IDataReader GetData(int i)
{
// need to think about this one
throw new NotImplementedException();
}
public virtual long GetBytes(int i, long fieldOffset, byte[] buffer, int bufferoffset, int length)
{
// need to keep track of the bytes got for each record - more work than i want to do right now
// http://msdn.microsoft.com/en-us/library/system.data.idatarecord.getbytes.aspx
throw new NotImplementedException();
}
public virtual long GetChars(int i, long fieldoffset, char[] buffer, int bufferoffset, int length)
{
// need to keep track of the bytes got for each record - more work than i want to do right now
// http://msdn.microsoft.com/en-us/library/system.data.idatarecord.getchars.aspx
throw new NotImplementedException();
}
#endregion
#region Implementation of IDataReader
public virtual void Close()
{
Closed = true;
}
public virtual DataTable GetSchemaTable()
{
var dt = new DataTable();
foreach (DynamicProperties.Property field in Fields)
{
dt.Columns.Add(new DataColumn(field.Info.Name, field.Info.PropertyType));
}
return dt;
}
public virtual bool NextResult()
{
throw new NotImplementedException();
}
public virtual int Depth
{
get { throw new NotImplementedException(); }
}
public virtual bool IsClosed
{
get { return Closed; }
}
public virtual int RecordsAffected
{
get
{
// assuming select only?
return -1;
}
}
#endregion
#region Implementation of IDisposable
public virtual void Dispose()
{
Fields = null;
}
#endregion
protected void SetFields(Type elementType)
{
Fields = DynamicProperties.CreatePropertyMethods(elementType);
}
}
}
// <copyright project="Salient.Reflection" file="DynamicProperties.cs" company="Sky Sanders">
// This source is a Public Domain Dedication.
// Please see http://spikes.codeplex.com/ for details.
// Attribution is appreciated
// </copyright>
// <version>1.0</version>
using System;
using System.Collections.Generic;
using System.Reflection;
using System.Reflection.Emit;
namespace Salient.Reflection
{
/// <summary>
/// Gets IL setters and getters for a property.
///
/// started with http://jachman.wordpress.com/2006/08/22/2000-faster-using-dynamic-method-calls/
/// </summary>
public static class DynamicProperties
{
#region Delegates
public delegate object GenericGetter(object target);
public delegate void GenericSetter(object target, object value);
#endregion
public static IList<Property> CreatePropertyMethods(Type T)
{
var returnValue = new List<Property>();
foreach (PropertyInfo prop in T.GetProperties())
{
returnValue.Add(new Property(prop));
}
return returnValue;
}
public static IList<Property> CreatePropertyMethods<T>()
{
var returnValue = new List<Property>();
foreach (PropertyInfo prop in typeof (T).GetProperties())
{
returnValue.Add(new Property(prop));
}
return returnValue;
}
/// <summary>
/// Creates a dynamic setter for the property
/// </summary>
/// <param name="propertyInfo"></param>
/// <returns></returns>
public static GenericSetter CreateSetMethod(PropertyInfo propertyInfo)
{
/*
* If there's no setter return null
*/
MethodInfo setMethod = propertyInfo.GetSetMethod();
if (setMethod == null)
return null;
/*
* Create the dynamic method
*/
var arguments = new Type[2];
arguments[0] = arguments[1] = typeof (object);
var setter = new DynamicMethod(
String.Concat("_Set", propertyInfo.Name, "_"),
typeof (void), arguments, propertyInfo.DeclaringType);
ILGenerator generator = setter.GetILGenerator();
generator.Emit(OpCodes.Ldarg_0);
generator.Emit(OpCodes.Castclass, propertyInfo.DeclaringType);
generator.Emit(OpCodes.Ldarg_1);
if (propertyInfo.PropertyType.IsClass)
generator.Emit(OpCodes.Castclass, propertyInfo.PropertyType);
else
generator.Emit(OpCodes.Unbox_Any, propertyInfo.PropertyType);
generator.EmitCall(OpCodes.Callvirt, setMethod, null);
generator.Emit(OpCodes.Ret);
/*
* Create the delegate and return it
*/
return (GenericSetter) setter.CreateDelegate(typeof (GenericSetter));
}
/// <summary>
/// Creates a dynamic getter for the property
/// </summary>
/// <param name="propertyInfo"></param>
/// <returns></returns>
public static GenericGetter CreateGetMethod(PropertyInfo propertyInfo)
{
/*
* If there's no getter return null
*/
MethodInfo getMethod = propertyInfo.GetGetMethod();
if (getMethod == null)
return null;
/*
* Create the dynamic method
*/
var arguments = new Type[1];
arguments[0] = typeof (object);
var getter = new DynamicMethod(
String.Concat("_Get", propertyInfo.Name, "_"),
typeof (object), arguments, propertyInfo.DeclaringType);
ILGenerator generator = getter.GetILGenerator();
generator.DeclareLocal(typeof (object));
generator.Emit(OpCodes.Ldarg_0);
generator.Emit(OpCodes.Castclass, propertyInfo.DeclaringType);
generator.EmitCall(OpCodes.Callvirt, getMethod, null);
if (!propertyInfo.PropertyType.IsClass)
generator.Emit(OpCodes.Box, propertyInfo.PropertyType);
generator.Emit(OpCodes.Ret);
/*
* Create the delegate and return it
*/
return (GenericGetter) getter.CreateDelegate(typeof (GenericGetter));
}
#region Nested type: Property
public class Property
{
public GenericGetter Getter;
public PropertyInfo Info;
public GenericSetter Setter;
public Property(PropertyInfo info)
{
Info = info;
Setter = CreateSetMethod(info);
Getter = CreateGetMethod(info);
}
}
#endregion
///// <summary>
///// An expression based Getter getter found in comments. untested.
///// Q: i don't see a reciprocal setter expression?
///// </summary>
///// <typeparam name="T"></typeparam>
///// <param name="propName"></param>
///// <returns></returns>
//public static Func<T> CreateGetPropValue<T>(string propName)
//{
// var param = Expression.Parameter(typeof(object), "container");
// var func = Expression.Lambda(
// Expression.Convert(Expression.PropertyOrField(Expression.Convert(param, typeof(T)), propName), typeof(object)), param);
// return (Func<T>)func.Compile();
//}
}
}
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