static Func <ObjContainer, T> CreateObjectGeneratorFromMapping <T>(IEnumerable <Attribute.FieldMapping> mapping)
{
var objectType = typeof(T);
var fields = TypeCache.GetProperties(objectType, true);
var parame = Expression.Parameter(typeof(ObjContainer), "par");
var memberBindings = new List <MemberBinding>();
//按顺序生成Binding
//int i = 0;
foreach (var mp in mapping)
{
if (!fields.ContainsKey(mp.FieldName))
{
continue;
}
var m = fields[mp.FieldName].GetPropertyInfo();
var method = ObjContainer.GetMethod(m.PropertyType, true);
//Expression getValue = Expression.Call(method, parame);
var getValue = parame.Call(method.Name, Expression.Constant(mp.ResultName));
if (m.PropertyType.IsEnum)
{
getValue = Expression.Convert(getValue, m.PropertyType);
}
var bind = (MemberBinding)Expression.Bind(m, getValue);
memberBindings.Add(bind);
//i += 1;
}
Expression expr = Expression.MemberInit(Expression.New(objectType), memberBindings);
var ret = Expression.Lambda <Func <ObjContainer, T> >(expr, parame);
return(ret.Compile());
}
List <TResult> QueryResultNewExpression <TModel, TResult>(LambdaQuery <TModel> query, NewExpression newExpression) where TModel : IModel, new()
{
//query.Select(newExpression);
var result = GetDynamicResult(query);
var list = new List <TResult>();
Func <ObjContainer, TResult> objCreater;
var parameters = newExpression.Constructor.GetParameters();
//当匿名类型指定了类型,没有构造参数
if (parameters.Length > 0)
{
objCreater = CreateObjectGenerator <TResult>(newExpression.Constructor);
}
else
{
objCreater = CreateObjectGeneratorFromMapping <TResult>(query.GetFieldMapping());
}
foreach (IDictionary <string, object> item in result)
{
var objC = new ObjContainer(item);
var obj = objCreater(objC);
list.Add(obj);
}
return(list);
}
static Func <ObjContainer, T> CreateObjectGenerator <T>(ConstructorInfo constructor)
{
var type = typeof(ObjContainer);
var parame = Expression.Parameter(type, "par");
var parameters = constructor.GetParameters();
List <Expression> arguments = new List <Expression>(parameters.Length);
foreach (var parameter in parameters)
{
var method = ObjContainer.GetMethod(parameter.ParameterType, true);
var getValue = Expression.Call(parame, method, Expression.Constant(parameter.Name));
arguments.Add(getValue);
}
var body = Expression.New(constructor, arguments);
var ret = Expression.Lambda <Func <ObjContainer, T> >(body, parame).Compile();
return(ret);
}
