更好的方式写这个linq查询Pt2
本文关键字:linq 查询 Pt2 方式写 更好 | 更新日期: 2023-09-27 18:01:29
对于这个问题的回答:
更好的方式来写这个linq查询?
我如何在该线程中建立一个遵循相同模式的动态查询?
例如,方法的签名更改为:
public List<PeopleSearchList> GetPeople(string filter, string searchType, string searchOption)
{
return a new List of type PeopleSearchList
}
所以现在我不是返回一个数组的"Firstnames"等,我返回一个自定义类。
这个类看起来像这样:
public class PeopleSearchList
{
public String IdentityCode { get; set; }
public String Firstname { get; set; }
public String Surname { get; set; }
public Int32 LoanCount { get; set; }
public String Group { get; set; }
}
我算出来了。
我只是想把解决方案贴出来给别人看看。
public List<PeopleSearchList> GetPeople(string filter, string searchType, string searchOption)
{
IQueryable<Person> query = _context.People;
PropertyInfo property = typeof (Person).GetProperty(searchType);
MethodInfo method = typeof (string).GetMethod(searchOption, new[] {typeof (string)});
query = query.Where(WhereExpression(property, method, filter));
IQueryable<PeopleSearchList> resultQuery = query.Select(p => new PeopleSearchList
{
Firstname = p.Firstname,
Group = p.Level.Year,
IdentityCode = p.IdentityCode,
LoanCount = p.Loans.Count(),
Surname = p.Surname
}
).OrderBy(p => p.Surname);
return resultQuery.ToList();
}
Expression<Func<Person, bool>> WhereExpression(PropertyInfo property, MethodInfo method, string filter)
{
var param = Expression.Parameter(typeof(Person), "o");
var propExpr = Expression.Property(param, property);
var methodExpr = Expression.Call(propExpr, method, Expression.Constant(filter));
return Expression.Lambda<Func<Person, bool>>(methodExpr, param);
}