从此帖子的代码中获取最新版本
没有什么比代码搅动显而易见的了：这是一个非常完整的实现。您可以通过IList IEnumerable，IEnumerable（ergo
IQueryable）实例化IDataReader。没有足够的理由在阅读器上公开通用类型参数，并且通过省略它，我可以允许IEnumerable
<’a>（匿名类型）。查看测试。
源代码（少了xmldocs）足够短，可以在此处进行一些测试。源，与xmldocs的休息，测试是
在这里
Salient.Data下。
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 }}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.preplex.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.preplex.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) { MethodInfo setMethod = propertyInfo.GetSetMethod(); if (setMethod == null) return null; 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); 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) { MethodInfo getMethod = propertyInfo.GetGetMethod(); if (getMethod == null) return null; 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); 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(); //} }}
