using System;
using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Linq.Expressions;
using System.Text;
using System.Threading.Tasks;
//
//2015-02-15
//1.修正记载增长了对 Nullable<int> 即int? 这类类型的支撑
namespace System.Data
{
/// <summary>
/// DataReader高性状读取帮肋类
/// </summary>
public class DataReaderFullHelper
{
/// <summary>
/// 读取DataReader填充数据
/// </summary>
/// <typeparam name="T">实体数据体</typeparam>
/// <param name="reader" />IDataReader对像
/// <param name="autoDisposeReader" />是不是在读取完成后主动释放DataReader
/// <returns></returns>
public List<t> FullListFromList<t>(IDataReader reader, bool autoDisposeReader = true) where T : new()
{
List<t> result = new List<t>();
try
{
Dictionary<int datacolumn=""> columnDics = new Dictionary<int datacolumn="">();
//表达式字典拜托
Dictionary<int, Action<t idatareader="">> actionDics = new Dictionary<int, Action<t idatareader="">>();
//数据实体类型
Type entityType = typeof(T);
var perDic = entityType.GetProperties().ToDictionary(p => p.Name);
//生成表头
for (int i = 0; i < reader.FieldCount; i++)
{
DataColumn col = new DataColumn()
{
ColumnName = reader.GetName(i),
DataType = reader.GetFieldType(i),
Namespace = reader.GetDataTypeName(i)
};
//添加列
columnDics.Add(i, col);
//如果包括列则进行添加
if (perDic.ContainsKey(col.ColumnName))
{
//获得字典值
var perty = perDic[col.ColumnName];
bool isnullable = IsNullableType(perty.PropertyType);
if (isnullable)
{
actionDics.Add(i, SetValueToEntity<t>(i, perty, col.DataType, isnullable));
}
else
{
actionDics.Add(i, SetValueToEntity<t>(i, col.ColumnName, col.DataType));
}
}
}
//查询读取项
while (reader.Read())
{
T objT = new T();
//添加到聚集
result.Add(objT);
//填充属性值
foreach (var item in actionDics)
{
//断定字段是不是为null
if (!reader.IsDBNull(item.Key))
{
//设置属性值
item.Value(objT, reader);
}
else
{
//null处置
}
}
}
}
finally
{
//释放dataReader
if (reader != null && autoDisposeReader)
{
reader.Close();
reader.Dispose();
}
}
return result;
}
#region 设置读取实体属性值
/// <summary>
/// nullable类型
/// </summary>
private Type nullableType = typeof(Nullable<>);
/// <summary>
/// 断定一个类型是不是为 Nullable 值类型
/// </summary>
/// <param name="theType" />值类型数据
/// <returns>是ull</returns>
public bool IsNullableType(Type theType)
{
return (theType.IsGenericType && theType.
GetGenericTypeDefinition().Equals
(nullableType));
}
/// <summary>
/// 返回null
/// </summary>
/// <typeparam name="T">值类型</typeparam>
/// <param name="par" />值数据
/// <returns></returns>
public static Func<T, Nullable<t>> ValueAction<t>() where T : struct
{
Func<T, Nullable<t>> fun = val => new Nullable<t>(val);
return fun;
}
/// <summary>
/// 获得指定索引的数据并且返回调用拜托
/// </summary>
/// <typeparam name="T">实体类类型</typeparam>
/// <typeparam name="T1">成果类型</typeparam>
/// <param name="index" />当前对应在DataReader中的索引
/// <param name="ProPertyName" />对应实体类属性名
/// <param name="FieldType" />字段类型
/// <returns>返回通过调用的拜托</returns>
public Action<t idatarecord=""> SetValueToEntity<t>(int index, string ProPertyName, Type FieldType)
{
Type datareader = typeof(IDataRecord);
IDataReader a;
var Mdthods = datareader.GetMethods().Where(p => p.ReturnType == FieldType && p.Name.StartsWith("Get") && p.GetParameters().Where(n => n.ParameterType == typeof(int)).Count() == 1);
//处置GetString办法
if (FieldType == typeof(string)) {
Mdthods = new System.Reflection.MethodInfo[] { datareader.GetMethod("GetString") };
}
//获得调用办法
System.Reflection.MethodInfo Method = null;
if (Mdthods.Count() > 0)
{
Method = Mdthods.FirstOrDefault();
}
else
{
throw new EntryPointNotFoundException("没有从DataReader找到适合的取值办法");
}
ParameterExpression e = Expression.Parameter(typeof(T), "e");
ParameterExpression r = Expression.Parameter(datareader, "r");
//常数表达式
ConstantExpression i = Expression.Constant(index);
MemberExpression ep = Expression.PropertyOrField(e, ProPertyName);
MethodCallExpression call = Expression.Call(r, Method, i);
//instance.Property = value 这名话是重点
BinaryExpression assignExpression = Expression.Assign(ep, call);
var ex = Expression.Lambda(assignExpression, e, r);
Expression<Action<t idatarecord="">> resultEx = Expression.Lambda<Action<t idatarecord="">>(assignExpression, e, r);
Action<t idatarecord=""> result = resultEx.Compile();
return result;
}
/// <summary>
/// 获得指定索引的数据并且返回调用拜托,用于处置Nullable值类型值
/// </summary>
/// <typeparam name="T">实体类类型</typeparam>
/// <typeparam name="T1">成果类型</typeparam>
/// <param name="index" />当前对应在DataReader中的索引
/// <param name="ProPertyName" />对应实体类属性名
/// <param name="FieldType" />字段类型
/// <param name="isNnullable" />是不是null值
/// <returns>返回通过调用的拜托</returns>
public Action<t idatarecord=""> SetValueToEntity<t>(int index, System.Reflection.PropertyInfo ProPerty, Type FieldType, bool isNnullable)
{
Action<t idatarecord=""> result;
//不是nullable正常返回
if (!isNnullable)
{
result = SetValueToEntity<t>(index, ProPerty.Name, FieldType);
}
else
{
//是 nullable 须要重新盘算
Type datareader = typeof(IDataRecord);
//获得值类型
var types = ProPerty.PropertyType.GetGenericArguments();
Type valType = null;
if (types.Length > 0)
{
valType = types[0];
}
//这个办法是获得值的功效
var Mdthods = datareader.GetMethods().Where(p => p.ReturnType == valType && p.Name.StartsWith("Get") && p.GetParameters().Where(n => n.ParameterType == typeof(int)).Count() == 1);
//处置GetString办法
if (FieldType == typeof(string))
{
Mdthods = new System.Reflection.MethodInfo[] { datareader.GetMethod("GetString") };
}
//获得调用办法
System.Reflection.MethodInfo Method = null;
if (Mdthods.Count() > 0)
{
Method = Mdthods.FirstOrDefault();
}
else
{
throw new EntryPointNotFoundException("没有从DataReader找到适合的取值办法");
}
//处置表达式
ParameterExpression e = Expression.Parameter(typeof(T), "e");
ParameterExpression r = Expression.Parameter(datareader, "r");
//常数表达式
ConstantExpression i = Expression.Constant(index);
MemberExpression ep = Expression.PropertyOrField(e, ProPerty.Name);
//调用dataReader的取值办法
MethodCallExpression call = Expression.Call(r, Method, i);
#region Nullable
//Nullable处置
var meth = GetType().GetMethod("ValueAction");
var genthod = meth.MakeGenericMethod(valType);
//调用办法生成拜托
Delegate thod = (Delegate)genthod.Invoke(null, null);
//将拜托邦定到表达式树 new Nullable<int>(121);
MethodCallExpression callNullable = Expression.Call(thod.Method, call);
#endregion
//处置值
BinaryExpression assignExpression = Expression.Assign(ep, callNullable);
var ex = Expression.Lambda(assignExpression, e, r);
Expression<Action<t idatarecord="">> resultEx = Expression.Lambda<Action<t idatarecord="">>(assignExpression, e, r);
result = resultEx.Compile();
}
return result;
}
/// <summary>
/// 获得指定索引的数据并且返回调用拜托
/// </summary>
/// <typeparam name="T">实体类类型</typeparam>
/// <typeparam name="T1">成果类型</typeparam>
/// <param name="index" />当前对应在DataReader中的索引
/// <param name="ProPertyName" />对应实体类属性名
/// <param name="canreturn" />是不是有返回值
/// <returns>返回通过调用的拜托</returns>
public Func<t idatareader="" t1=""> SetValueToEntity<t t1="">(int index, string ProPertyName)
{
Type datareader = typeof(IDataRecord);
var Mdthods = datareader.GetMethods().Where(p => p.ReturnType == typeof(T1));
//获得调用办法
System.Reflection.MethodInfo Method = null;
if (Mdthods.Count() > 0)
{
Method = Mdthods.FirstOrDefault();
}
else
{
throw new EntryPointNotFoundException("没有从DataReader找到适合的取值办法");
}
ParameterExpression e = Expression.Parameter(typeof(T), "e");
ParameterExpression r = Expression.Parameter(datareader, "r");
//常数表达式
ConstantExpression i = Expression.Constant(index);
MemberExpression ep = Expression.PropertyOrField(e, ProPertyName);
MethodCallExpression call = Expression.Call(r, Method, i);
//instance.Property = value 这句话是重点
BinaryExpression assignExpression = Expression.Assign(ep, call);
var ex = Expression.Lambda(assignExpression, e, r);
Expression<Func<t idatarecord="" t1="">> resultEx = Expression.Lambda<Func<t idatarecord="" t1="">>(assignExpression, e, r);
Func<t idatarecord="" t1=""> result = resultEx.Compile();
return result;
}
/// <summary>
/// 获得设置DataRead与实体类指定列的表达式
/// </summary>
/// <typeparam name="T">实体类类型</typeparam>
/// <typeparam name="T1">成果类型</typeparam>
/// <param name="index" />当前对应在DataReader中的索引
/// <param name="ProPertyName" />对应实体类属性名
/// <param name="DataReaderGetValueMethodName" />调用DataReader中获得值的办法名如:GetString
/// <returns>返回通过调用的拜托</returns>
public Func<t idatareader="" t1=""> SetValueToEntity<t t1="">(int index, string ProPertyName, string DataReaderGetValueMethodName)
{
ParameterExpression e = Expression.Parameter(typeof(T), "e");
ParameterExpression r = Expression.Parameter(typeof(IDataRecord), "r");
//常数表达式
ConstantExpression i = Expression.Constant(index);
MemberExpression ep = Expression.PropertyOrField(e, ProPertyName);
MethodCallExpression call = Expression.Call(r, typeof(IDataRecord).GetMethod(DataReaderGetValueMethodName, new Type[] { typeof(int) }), i);
//instance.Property = value 这名话是重点
BinaryExpression assignExpression = Expression.Assign(ep, call);
var ex = Expression.Lambda(assignExpression, e, r);
Expression<Func<t idatarecord="" t1="">> resultEx = Expression.Lambda<Func<t idatarecord="" t1="">>(assignExpression, e, r);
Func<t idatarecord="" t1=""> result = resultEx.Compile();
return result;
}
/// <summary>
/// 获得设置属性值的拜托
/// </summary>
/// <typeparam name="T">当关类型名</typeparam>
/// <typeparam name="T1">返回值</typeparam>
/// <param name="index" />索引
/// <param name="Entity" />实体对像
/// <param name="ProPertyName" />属性名
/// <param name="DataReaderGetValueMethodName" />DataReader获得值办法名 如:"GetString"
/// <returns></returns>
public Func<t idatarecord="" t1="" int=""> SetPropertyValue<t t1="">(int index, T Entity, string ProPertyName, string DataReaderGetValueMethodName)
{
//(e, r, index) => (e.bookname = r.GetString(index))
ParameterExpression e = Expression.Parameter(typeof(T), "e");
ParameterExpression r = Expression.Parameter(typeof(IDataRecord), "r");
ParameterExpression i = Expression.Parameter(typeof(int), "index");
MemberExpression ep = Expression.PropertyOrField(e, ProPertyName);
MethodCallExpression call = Expression.Call(r, typeof(IDataRecord).GetMethod(DataReaderGetValueMethodName, new Type[] { typeof(int) }), i);
//instance.Property = value 这名话是重点
BinaryExpression assignExpression = Expression.Assign(ep, call);
var ex = Expression.Lambda(assignExpression, e, r, i);
Expression<Func<t idatarecord="" t1="" int="">> resultEx = Expression.Lambda<Func<t idatarecord="" t1="" int="">>(assignExpression, e, r, i);
Func<t idatarecord="" t1="" int=""> result = resultEx.Compile();
return result;
}
/// <summary>
/// https://zhidao.baidu.com/link?url=CdGxWD3l5r9H84NPWRSBFtNkea0hn5g0YujI3AIIPUO0W6g4OHxeunQN6qW2Awq2noM2Mfnj1GrD3FOOagamtwIo67ZVK7M6hj_QiwfEJX7
/// sdd = sdd.Where(s => s.SKUCoding.Split("-").Contains(t));
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="entity" />
/// <param name="propertyname" />
/// <param name="value" />
/// <returns></returns>
private IEnumerable<t> SearchTcontains<t>(IQueryable<t> entity, string propertyname, string value)// where T : EntityObject
{
// NorthwindEntities en = new NorthwindEntities();
ParameterExpression pe = Expression.Parameter(typeof(T), "c");
MemberExpression me = Expression.Property(pe, "CustomerID");
ConstantExpression ce = Expression.Constant(value);
Expression right = Expression.Call(
me,
//
typeof(string).GetMethod("Contains", new Type[] { typeof(string) }),
ce);
Expression<Func<t bool="">> p = Expression.Lambda<Func<t bool="">>(right, pe);
// IEnumerable<t> ems = en.CreateQuery<t>(Plural<t>()).Where(p);
// return ems as IEnumerable<t>;
return null;
}
#endregion
}
/// <summary>
/// DataReader扩大办法
/// </summary>
public static class DataReaderReadExtend
{
/// <summary>
/// 实体赞助类
/// </summary>
private static DataReaderFullHelper hepler = new DataReaderFullHelper();
/// <summary>
/// 读取Data的扩大办法
/// </summary>
/// <typeparam name="T">实体数据体</typeparam>
/// <param name="reader" />IDataReader对像
/// <param name="autoDisposeReader" />是不是在读取完成后主动释放DataReader
/// <returns></returns>
public static List<t> ReaderToList<t>(this IDataReader reader, bool autoDisposeReader = true) where T : new()
{
return hepler.FullListFromList<t>(reader, autoDisposeReader);
}
}
}
</t></t></t></t></t></t></t></t></t></t></t></t></t></t></t></t></t></t></t></t></t></t></t></t></t></t></t></t></t></int></t></t></t></t></t></t></t></t></t></t></t></t></t></t></t></t></t></int></int></t></t></t></t></int>using System;
using System;
using System.Collecti
阅读背景：
支持 Nullable的DataReader高效转实体代码
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