expression select表达式动态构建

参考：

http://blog.csdn.net/tastelife/article/details/7340205

http://blog.csdn.net/sweety820/article/details/39203087

源码：

private static Expression<Func<TSource, TResult>> CreateSelecter<TSource, TResult>(Dictionary<string,string> fieldDic)
{
Expression<Func<TSource, TResult>> selector = null;

//(rec)
ParameterExpression param = Expression.Parameter(typeof(TSource), "x");
//new ParadigmSearchListData
var v0 = Expression.New(typeof(TResult));
//Number
List<MemberBinding> bindingList = new List<MemberBinding>();
foreach (var item in fieldDic)
{
var p = typeof(TResult).GetProperty(item.Key);
Expression right = GetProperty<TSource>(null, item.Value, param);
//right= Expression.Constant(right, p.PropertyType);
var v = Expression.Convert(GetProperty<TSource>(null, item.Value, param), p.PropertyType);
var m = Expression.Bind(p, v);
bindingList.Add(m);
}
Expression body = Expression.MemberInit(v0, bindingList);

selector = (Expression<Func<TSource, TResult>>)Expression.Lambda(body, param);

return selector;
}

public static Expression GetProperty<T>(Expression source, string Name, ParameterExpression Param)
{
Name = Name.Replace(")", "");
string[] propertys = null;
if (Name.Contains("=>"))
{
propertys = Name.Split('.').Skip(1).ToArray();
}
else
{
propertys = Name.Split('.');
}
if (source == null)
{
source = Expression.Property(Param, typeof(T).GetProperty(propertys.First()));
}
else
{
source = Expression.Property(source, propertys.First());
}
foreach (var item in propertys.Skip(1))
{
source = GetProperty<T>(source, item, Param);
}
return source;
}

巴特西

expression select表达式动态构建

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