linq

问题 I have a database with a User's and Role's table. Each user can be in lots of roles, so there is a 'middle' table called UserRoles that simply contains a RoleId and UserId. Now I need to get all the roles attached to a User. public IEnumerable<Role> GetAllRoles(int UserId) { var query = from R in _db.Roles where RolesTbl.UserRoles.UserId == UserId select R; return query; } Now the query above doesnt work, "RolesTbl.UserRoles.UserId" I cant referance it in this way because of the Many to Many.

问题 Our mvc project with json.net running without any problem on every developer except the one with the new windows 8.1 system. How can we find source of the method not found problem ? details of the exception ; [MissingMethodException: Method not found: 'System.Object Newtonsoft.Json.Linq.JToken.ToObject(System.Type)'.] ExtensionMethods.Eval(Object o, String propertyName) in c:\Users\maxSEPHIROTH\Documents\Visual Studio 2012\Projects\LogiSysMvc\LogiSysMvc\ClassLibrary\ExtensionMethods.cs:136

问题 I am trying to Order by a query using the following efcore query Getting the PropertyInfo for the column which needs to be orderedBy using this below var propertyInfo = typeof(TableVM).GetProperty("Type"); The EfCore Query db.Table **//LinkKit Extension Method** .AsExpandable() .Where(whereClause) .Select(m => new TableVM { id= m.Id, name = m.Name, description = m.Description, type = m.Type, status = m.Status }) **// Conversion of the OrderBy fails, which throws an exception saying it can't

问题 I am trying to Order by a query using the following efcore query Getting the PropertyInfo for the column which needs to be orderedBy using this below var propertyInfo = typeof(TableVM).GetProperty("Type"); The EfCore Query db.Table **//LinkKit Extension Method** .AsExpandable() .Where(whereClause) .Select(m => new TableVM { id= m.Id, name = m.Name, description = m.Description, type = m.Type, status = m.Status }) **// Conversion of the OrderBy fails, which throws an exception saying it can't

问题 How to use Multiple value with Contain in Dynamic Linq. Expected With Normal Linq : using System; using System.Linq; public class Simple { public static void Main() { string[] names = { "Burke", "Laptop", "Computer", "Mobile", "Ahemed", "Sania", "Kungada", "David","United","Sinshia" }; string[] vars = {"i","a"}; var query = names.Where(i=> vars.Any(j=>i.Contains(j))).ToList(); Console.WriteLine(query.Count); } } Expected SQL SELECT * FROM User WHERE (NAME LIKE '%a%'OR NAME LIKE '%b%') Tried

问题 Good morning, I wrote the following LINQ query public static Func<String, IEnumerable<String>> ListaCorreccoes = (StrPalavra) => { return (from StrTmp in ListaPossiveisCorreccoes(StrPalavra) from StrTmp2 in ListaPossiveisCorreccoes(StrTmp) where PalavraConhecida(StrTmp2) select StrTmp2).Distinct(); }; which, to my surprise, is much faster than using two foreach cicles. After running this function using ListaTmp = ListaCorreccoes("comutador"); , where ListaTmp is of type IEnumerable<String> ,

问题 Good morning, I wrote the following LINQ query public static Func<String, IEnumerable<String>> ListaCorreccoes = (StrPalavra) => { return (from StrTmp in ListaPossiveisCorreccoes(StrPalavra) from StrTmp2 in ListaPossiveisCorreccoes(StrTmp) where PalavraConhecida(StrTmp2) select StrTmp2).Distinct(); }; which, to my surprise, is much faster than using two foreach cicles. After running this function using ListaTmp = ListaCorreccoes("comutador"); , where ListaTmp is of type IEnumerable<String> ,

问题 I have a table with localized values like this LocalizedFruits ID | LOCALE | NAME 1 | en_UK | Banana 2 | da_DK | Banan 3 | de_DE | Banane 4 | zh-CHS | 香蕉 Then i want to autocomplete the value the user is typing, if the user is chinese it's all good but if it's people from one of the other cultures a problem arises, when they type "ba" the user will get 3 results that are the same thing. therefore i group the result by Locale. What i want to do is i want to get the group with the same locale

问题 I have a table with localized values like this LocalizedFruits ID | LOCALE | NAME 1 | en_UK | Banana 2 | da_DK | Banan 3 | de_DE | Banane 4 | zh-CHS | 香蕉 Then i want to autocomplete the value the user is typing, if the user is chinese it's all good but if it's people from one of the other cultures a problem arises, when they type "ba" the user will get 3 results that are the same thing. therefore i group the result by Locale. What i want to do is i want to get the group with the same locale

问题 Application accidentally crashed with stack overflow error. After research I found that the reason of crash is following code: foreach (var item in items) { result = result.Concat(item.Data); } This is concatenation of multiple IEnumerable s. Application crashed when items contained 10,000 elements. SelectMany fixed this issue. But still... Why Concat extension causes stack overflow here? 回答1: Remember that the result of Concat is not a collection - it's a query . So your "result" is