private static ReadFieldInfo[] GetDataReaderFieldInfo(IDataReader Reader)
{
ReadFieldInfo[] Fields = new ReadFieldInfo[Reader.FieldCount];
var count = Reader.FieldCount;
for (int i = 0; i < count; i++)
{
Type dbType = Reader.GetFieldType(i);
Type CsType;
//////不同数据库类型与CSharp类型对应
if (DBTypeMapping.TryGetValue(dbType, out CsType))
{
Fields[i] = new ReadFieldInfo()
{
FieldIndex = i, FieldName = Reader.GetName(i), FieldType = CsType
};
}
else
{
Fields[i] = new ReadFieldInfo()
{
FieldIndex = i, FieldName = Reader.GetName(i), FieldType = dbType
};
}
}
return(Fields);
}
public static Func <IDataReader, T> GetCreator <T>(IDataReader Reader)
{
object func = null;
Type classType = typeof(T);
ReadFieldInfo[] FieldInfos = GetDataReaderFieldInfo(Reader);
StringBuilder sber = new StringBuilder().Append(classType.GetHashCode());
for (int c = 0; c < FieldInfos.Length; c++)
{
sber.Append(FieldInfos[c].FieldType.Name);
}
if (CreatorsCache.TryGetValue(sber.ToString(), out func))
{
return((Func <IDataReader, T>)func);
}
var ppIndex = new List <ODAPropertyInfo>();
PropertyInfo[] prptys = classType.GetProperties(BindingFlags.Instance | BindingFlags.Public);
for (int i = 0; i < prptys.Length; i++)
{
if (prptys[i].CanWrite)
{
ppIndex.Add(new ODAPropertyInfo(prptys[i]));
}
}
DynamicMethod method;
if (classType.IsInterface)
{
method = new DynamicMethod("Create" + classType.Name, classType, new Type[] { typeof(IDataReader) }, classType.Module, true);
}
else
{
method = new DynamicMethod("Create" + classType.Name, classType, new Type[] { typeof(IDataReader) }, classType, true);
}
ILGenerator il = method.GetILGenerator();
LocalBuilder result = il.DeclareLocal(classType);
il.Emit(OpCodes.Nop);
il.Emit(OpCodes.Newobj, classType.GetConstructor(Type.EmptyTypes));
il.Emit(OpCodes.Stloc, result);
for (int i = 0; i < ppIndex.Count; i++)
{
ReadFieldInfo Field = null;
foreach (var fld in FieldInfos)
{
if (fld.FieldName == ppIndex[i].PropertyName)
{
Field = fld;
break;
}
}
var setter = ppIndex[i].OriginProperty.GetSetMethod(true);
if (setter != null && Field != null)
{
Label lb = il.DefineLabel();
il.Emit(OpCodes.Ldarg_0);
il.Emit(OpCodes.Ldc_I4, Field.FieldIndex);
il.Emit(OpCodes.Callvirt, IsDBNull);
il.Emit(OpCodes.Brtrue, lb);
il.Emit(OpCodes.Ldloc, result);
il.Emit(OpCodes.Ldarg_0);
il.Emit(OpCodes.Ldc_I4, Field.FieldIndex);
BindReaderMethod(il, ppIndex[i], Field.FieldType);
if (setter.IsFinal || !setter.IsVirtual)
{
il.Emit(OpCodes.Call, setter);
}
else
{
il.Emit(OpCodes.Callvirt, setter);
}
il.MarkLabel(lb);
}
}
il.Emit(OpCodes.Ldloc, result);
il.Emit(OpCodes.Ret);
object reator = method.CreateDelegate(typeof(Func <IDataReader, T>));
CreatorsCache.Add(sber.ToString(), reator);
GC.KeepAlive(reator);
return((Func <IDataReader, T>)reator);
}
