private static Func <IDataRecord, T> CreateTypeSerializerHandler <T>(ITypeMapper mapper, IDataRecord record)
{
var type = typeof(T);
var methodName = $"{type.Name}Serializer{Guid.NewGuid().ToString("N")}";
var dynamicMethod = new DynamicMethod(methodName, type, new Type[] { typeof(IDataRecord) }, type, true);
var generator = dynamicMethod.GetILGenerator();
LocalBuilder local = generator.DeclareLocal(type);
var dataInfos = new DbDataInfo[record.FieldCount];
for (int i = 0; i < record.FieldCount; i++)
{
var dataname = record.GetName(i);
var datatype = record.GetFieldType(i);
var typename = record.GetDataTypeName(i);
dataInfos[i] = new DbDataInfo(i, typename, datatype, dataname);
}
if (dataInfos.Length == 1 && (type.IsValueType || type == typeof(string) || type == typeof(object)))
{
var dataInfo = dataInfos.First();
var convertMethod = mapper.FindConvertMethod(type, dataInfo.DataType);
generator.Emit(OpCodes.Ldarg_0);
generator.Emit(OpCodes.Ldc_I4, 0);
if (convertMethod.IsVirtual)
{
generator.Emit(OpCodes.Callvirt, convertMethod);
}
else
{
generator.Emit(OpCodes.Call, convertMethod);
}
generator.Emit(OpCodes.Stloc, local);
generator.Emit(OpCodes.Ldloc, local);
generator.Emit(OpCodes.Ret);
return(dynamicMethod.CreateDelegate(typeof(Func <IDataRecord, T>)) as Func <IDataRecord, T>);
}
var constructor = mapper.FindConstructor(type);
if (constructor.GetParameters().Length > 0)
{
var parameters = constructor.GetParameters();
var locals = new LocalBuilder[parameters.Length];
for (int i = 0; i < locals.Length; i++)
{
locals[i] = generator.DeclareLocal(parameters[i].ParameterType);
}
for (int i = 0; i < locals.Length; i++)
{
var item = mapper.FindConstructorParameter(dataInfos, parameters[i]);
if (item == null)
{
continue;
}
var convertMethod = mapper.FindConvertMethod(parameters[i].ParameterType, item.DataType);
generator.Emit(OpCodes.Ldarg_0);
generator.Emit(OpCodes.Ldc_I4, item.Ordinal);
if (convertMethod.IsVirtual)
{
generator.Emit(OpCodes.Callvirt, convertMethod);
}
else
{
generator.Emit(OpCodes.Call, convertMethod);
}
generator.Emit(OpCodes.Stloc, locals[i]);
}
for (int i = 0; i < locals.Length; i++)
{
generator.Emit(OpCodes.Ldloc, locals[i]);
}
generator.Emit(OpCodes.Newobj, constructor);
generator.Emit(OpCodes.Stloc, local);
generator.Emit(OpCodes.Ldloc, local);
generator.Emit(OpCodes.Ret);
return(dynamicMethod.CreateDelegate(typeof(Func <IDataRecord, T>)) as Func <IDataRecord, T>);
}
else
{
var properties = type.GetProperties();
generator.Emit(OpCodes.Newobj, constructor);
generator.Emit(OpCodes.Stloc, local);
foreach (var item in dataInfos)
{
var property = mapper.FindMember(properties, item) as PropertyInfo;
if (property == null)
{
continue;
}
var convertMethod = mapper.FindConvertMethod(property.PropertyType, item.DataType);
if (convertMethod == null)
{
continue;
}
int i = record.GetOrdinal(item.DataName);
generator.Emit(OpCodes.Ldloc, local);
generator.Emit(OpCodes.Ldarg_0);
generator.Emit(OpCodes.Ldc_I4, i);
if (convertMethod.IsVirtual)
{
generator.Emit(OpCodes.Callvirt, convertMethod);
}
else
{
generator.Emit(OpCodes.Call, convertMethod);
}
generator.Emit(OpCodes.Callvirt, property.GetSetMethod());
}
generator.Emit(OpCodes.Ldloc, local);
generator.Emit(OpCodes.Ret);
return(dynamicMethod.CreateDelegate(typeof(Func <IDataRecord, T>)) as Func <IDataRecord, T>);
}
}