完整源代码购买：http://livexy.taobao.com/
IDataReader扩展ToList<T> 改进版
//最快和直接循环差不多
public static List<TResult> ToList<TResult>(this IDataReader dr, bool isClose) where TResult : class, new() {
IDataReaderEntityBuilder<TResult> eblist = IDataReaderEntityBuilder<TResult>.CreateBuilder(dr);
List<TResult> list = new List<TResult>();
if (dr == null) return list;
while (dr.Read()) list.Add(eblist.Build(dr));
if (isClose) { dr.Close(); dr.Dispose(); dr = null; }
return list;
}
public static List<TResult> ToList<TResult>(this IDataReader dr) where TResult : class, new() {
return dr.ToList<TResult>(true);
}
//也慢
public static List<TResult> ToList2<TResult>(this IDataReader dr, bool isClose) where TResult : class, new() {
List<TResult> oblist = new List<TResult>();
if (dr == null) return oblist;
List<string> drColumns = new List<string>();
int len = dr.FieldCount;
for (int j = 0; j < len; j++) drColumns.Add(dr.GetName(j).Trim());
List<PropertyInfo> prlist = new List<PropertyInfo>();
Type t = typeof(TResult);
Array.ForEach<PropertyInfo>(t.GetPropertiesCache(), p => { if (drColumns.IndexOf(p.Name) != -1) prlist.Add(p); });
while (dr.Read()) {
TResult ob = new TResult();
prlist.ForEach(p => { if (dr[p.Name] != DBNull.Value) p.SetValue(ob, dr[p.Name], null); });
oblist.Add(ob);
}
if (isClose) { dr.Close(); dr.Dispose(); dr = null; }
return oblist;
}
public static List<TResult> ToList2<TResult>(this IDataReader dr) where TResult : class, new() {
return dr.ToList2<TResult>(true);
}
//最慢
public static List<TResult> ToList3<TResult>(this IDataReader dr, bool isClose) where TResult : class, new() {
List<TResult> list = new List<TResult>();
if (dr == null) return list;
int len = dr.FieldCount;
while (dr.Read()) {
TResult info = new TResult();
for (int j = 0; j < len; j++) {
if (dr[j] == null || string.IsNullOrEmpty(dr[j].ToString())) continue;
info.GetType().GetPropertyCache(dr.GetName(j).Trim()).SetValue(info, dr[j], null);
}
list.Add(info);
}
if (isClose) { dr.Close(); dr.Dispose(); dr = null; }
return list;
}
public static List<TResult> ToList3<TResult>(this IDataReader dr) where TResult : class, new() {
return dr.ToList3<TResult>(true);
}
谢谢""提供更快速的DataReader转实体LIST的代码.我将发在这里:
public class IDataReaderEntityBuilder<Entity> {
private static readonly MethodInfo getValueMethod =
typeof(IDataRecord).GetMethod("get_Item", new Type[] { typeof(int) });
private static readonly MethodInfo isDBNullMethod =
typeof(IDataRecord).GetMethod("IsDBNull", new Type[] { typeof(int) });
private delegate Entity Load(IDataRecord dataRecord);
private Load handler;
private IDataReaderEntityBuilder() { }
public Entity Build(IDataRecord dataRecord) {
return handler(dataRecord);
}
public static IDataReaderEntityBuilder<Entity> CreateBuilder(IDataRecord dataRecord) {
IDataReaderEntityBuilder<Entity> dynamicBuilder = new IDataReaderEntityBuilder<Entity>();
DynamicMethod method = new DynamicMethod("DynamicCreateEntity", typeof(Entity),
new Type[] { typeof(IDataRecord) }, typeof(Entity), true);
ILGenerator generator = method.GetILGenerator();
LocalBuilder result = generator.DeclareLocal(typeof(Entity));
generator.Emit(OpCodes.Newobj, typeof(Entity).GetConstructor(Type.EmptyTypes));
generator.Emit(OpCodes.Stloc, result);
for (int i = 0; i < dataRecord.FieldCount; i++) {
PropertyInfo propertyInfo = typeof(Entity).GetProperty(dataRecord.GetName(i));
Label endIfLabel = generator.DefineLabel();
if (propertyInfo != null && propertyInfo.GetSetMethod() != null) {
generator.Emit(OpCodes.Ldarg_0);
generator.Emit(OpCodes.Ldc_I4, i);
generator.Emit(OpCodes.Callvirt, isDBNullMethod);
generator.Emit(OpCodes.Brtrue, endIfLabel);
generator.Emit(OpCodes.Ldloc, result);
generator.Emit(OpCodes.Ldarg_0);
generator.Emit(OpCodes.Ldc_I4, i);
generator.Emit(OpCodes.Callvirt, getValueMethod);
generator.Emit(OpCodes.Unbox_Any, dataRecord.GetFieldType(i));
generator.Emit(OpCodes.Callvirt, propertyInfo.GetSetMethod());
generator.MarkLabel(endIfLabel);
}
}
generator.Emit(OpCodes.Ldloc, result);
generator.Emit(OpCodes.Ret);
dynamicBuilder.handler = (Load)method.CreateDelegate(typeof(Load));
return dynamicBuilder;
}
}
使用反射的同志们，请放泣使用反射方法转实体类LIST.
DataTable扩展ToList<T> 改进版
//最快和直接循环差不多
public static List<TResult> ToList<TResult>(this DataTable dt) where TResult : class, new() {
List<TResult> list = new List<TResult>();
if (dt == null) return list;
DataTableEntityBuilder<TResult> eblist = DataTableEntityBuilder<TResult>.CreateBuilder(dt.Rows[0]);
foreach(DataRow info in dt.Rows) list.Add(eblist.Build(info));
dt.Dispose(); dt = null;
return list;
}
//也慢
public static List<TResult> ToList2<TResult>(this DataTable dt) where TResult : class, new() {
List<PropertyInfo> prlist = new List<PropertyInfo>();
Type t = typeof(TResult);
Array.ForEach<PropertyInfo>(t.GetPropertiesCache(), p => { if (dt.Columns.IndexOf(p.Name) != -1) prlist.Add(p); });
List<TResult> oblist = new List<TResult>();
foreach (DataRow row in dt.Rows) {
TResult ob = new TResult();
prlist.ForEach(p => { if (row[p.Name] != DBNull.Value) p.SetValue(ob, row[p.Name], null); });
oblist.Add(ob);
}
return oblist;
}
//最慢
public static List<TResult> ToList3<TResult>(this DataTable dt) where TResult : class, new() {
List<TResult> list = new List<TResult>();
if (dt == null) return list;
int len = dt.Rows.Count;
for (int i = 0; i < len; i++) {
TResult info = new TResult();
foreach (DataColumn dc in dt.Rows[0].Table.Columns) {
if (dt.Rows[i][dc.ColumnName] == null || string.IsNullOrEmpty(dt.Rows[i][dc.ColumnName].ToString())) continue;
info.GetType().GetPropertyCache(dc.ColumnName).SetValue(info, dt.Rows[i][dc.ColumnName], null);
}
list.Add(info);
}
dt.Dispose(); dt = null;
return list;
}
public class DataTableEntityBuilder<Entity> {
private static readonly MethodInfo getValueMethod = typeof(DataRow).GetMethod("get_Item", new Type[] { typeof(int) });
private static readonly MethodInfo isDBNullMethod = typeof(DataRow).GetMethod("IsNull", new Type[] { typeof(int) });
private delegate Entity Load(DataRow dataRecord);
private Load handler;
private DataTableEntityBuilder() { }
public Entity Build(DataRow dataRecord) {
return handler(dataRecord);
}
public static DataTableEntityBuilder<Entity> CreateBuilder(DataRow dataRecord) {
DataTableEntityBuilder<Entity> dynamicBuilder = new DataTableEntityBuilder<Entity>();
DynamicMethod method = new DynamicMethod("DynamicCreateEntity", typeof(Entity), new Type[] { typeof(DataRow) }, typeof(Entity), true);
ILGenerator generator = method.GetILGenerator();
LocalBuilder result = generator.DeclareLocal(typeof(Entity));
generator.Emit(OpCodes.Newobj, typeof(Entity).GetConstructor(Type.EmptyTypes));
generator.Emit(OpCodes.Stloc, result);
for (int i = 0; i < dataRecord.ItemArray.Length; i++) {
PropertyInfo propertyInfo = typeof(Entity).GetProperty(dataRecord.Table.Columns[i].ColumnName);
Label endIfLabel = generator.DefineLabel();
if (propertyInfo != null && propertyInfo.GetSetMethod() != null) {
generator.Emit(OpCodes.Ldarg_0);
generator.Emit(OpCodes.Ldc_I4, i);
generator.Emit(OpCodes.Callvirt, isDBNullMethod);
generator.Emit(OpCodes.Brtrue, endIfLabel);
generator.Emit(OpCodes.Ldloc, result);
generator.Emit(OpCodes.Ldarg_0);
generator.Emit(OpCodes.Ldc_I4, i);
generator.Emit(OpCodes.Callvirt, getValueMethod);
generator.Emit(OpCodes.Unbox_Any, propertyInfo.PropertyType);
generator.Emit(OpCodes.Callvirt, propertyInfo.GetSetMethod());
generator.MarkLabel(endIfLabel);
}
}
generator.Emit(OpCodes.Ldloc, result);
generator.Emit(OpCodes.Ret);
dynamicBuilder.handler = (Load)method.CreateDelegate(typeof(Load));
return dynamicBuilder;
}
}
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