//DataReader로 부터 값들을 읽어 인스턴스를 만든다
private ConstructInstance CreateConstructInstance(IDataReader reader)
{
ParameterException.Check(reader != null, ParameterError.NotExistReader);
var type = typeof(T);
var dynamicMethod = new DynamicMethod("ConstructInstance", type, new[] { typeof(IDataReader) }, type);
var il = dynamicMethod.GetILGenerator();
Label startLoop = il.DefineLabel();
Label endLoop = il.DefineLabel();
ConstructorInfo constructor = type.GetConstructor(Type.EmptyTypes);
il.Emit(OpCodes.Newobj, constructor); //[instance]
il.MarkLabel(startLoop);
PropertyInfo[] properties = type.GetProperties(BindingFlags.Public | BindingFlags.Instance);
foreach (PropertyInfo property in properties)
{
Label startValueTypeNullLoop = il.DefineLabel();
Label endValueTypeNullLoop = il.DefineLabel();
Label jumpToEnd = il.DefineLabel();
var columnAttribute = property.GetCustomAttribute <ColumnAttribute>();
AttributeException.Check(columnAttribute != null, AttributeError.NotExistColumnAttribute);
var columnName = columnAttribute.Name ?? property.Name;
//SetValue
il.Emit(OpCodes.Dup); //[instance][instance]
il.Emit(OpCodes.Ldarg_0); //[instance][instance][IDataReader]
il.Emit(OpCodes.Ldstr, columnName); //[instance][instance][IDataReader][Name]
il.Emit(OpCodes.Call,
typeof(IDataReaderHelper).GetMethod(nameof(IDataReaderHelper
.GetValue))); //[instance][instance][value]
il.Emit(OpCodes.Dup); //[instance][instance][value][value]
il.Emit(OpCodes.Ldsfld,
typeof(DBNull).GetField(nameof(DBNull.Value))); //[instance][instance][value][value][DBNullValue]
il.Emit(OpCodes.Ceq); // [instance][instance][value][result]
il.Emit(OpCodes.Brtrue, startValueTypeNullLoop); //[instance][instance]
if (property.PropertyType.IsValueType)
{
il.Emit(OpCodes.Unbox_Any, property.PropertyType); //[instance][instance][unbox_value]
}
il.MarkLabel(endValueTypeNullLoop);
il.Emit(OpCodes.Call, property.GetSetMethod()); //[instance]
il.Emit(OpCodes.Br, jumpToEnd);
il.MarkLabel(startValueTypeNullLoop);
if (property.PropertyType.IsValueType)
{
il.Emit(OpCodes.Pop); //[instance][instance]
il.Emit(OpCodes.Ldc_I4_0); //[instance][instance][0]
}
il.Emit(OpCodes.Br, endValueTypeNullLoop);
il.MarkLabel(jumpToEnd);
}
il.MarkLabel(endLoop);
il.Emit(OpCodes.Ret);
return((ConstructInstance)dynamicMethod.CreateDelegate(typeof(ConstructInstance)));
}
