linq-expressions

问题 I'm struggling to dynamically create a query like that: Dictionary<string, Guid> parms = new Dictionary<string, Guid>(); foreach (var kvp in parms) { var exp = ReportDefinitions.Where(x=> x.Discriminants.Any(y=> y.Key == kvp.Key && y.Value == kvp.Value) // && more conditions to add here at each cycle ); } Where ReportDefinitions.Discriminants is an IDictionary<string, Guid> ; I know how to build simple Expression but I can't figure out how to build this one the "Any" seems really complicated.

问题 Question: I have this C# program, that gets the value of field tablename of mytable. And it works fine. using System; using System.Collections.Generic; using System.Linq; using System.Windows.Forms; namespace AttachObjectsCS { static class Program { public class cmytable { public string tablename = "test"; } // http://stackoverflow.com/questions/2616638/access-the-value-of-a-member-expression private static object GetValue(System.Linq.Expressions.MemberExpression member) { System.Linq

问题 Question: I have this C# program, that gets the value of field tablename of mytable. And it works fine. using System; using System.Collections.Generic; using System.Linq; using System.Windows.Forms; namespace AttachObjectsCS { static class Program { public class cmytable { public string tablename = "test"; } // http://stackoverflow.com/questions/2616638/access-the-value-of-a-member-expression private static object GetValue(System.Linq.Expressions.MemberExpression member) { System.Linq

问题 i'm writing mvc app in .net core, i have problem with localization, i don't know how to add IViewLocalizer to my grid view. Here is my code: @using NonFactors.Mvc.Grid; @using Microsoft.AspNetCore.Mvc.Localization @inject IViewLocalizer Localizer @model IEnumerable<WeegreeEmployeeFormsCore.Models.Employee> @(Html .Grid(Model) .Build(columns => { columns.Add(model => model.Name).Titled(Localizer["Name"]).Sortable(true).Filterable(true); columns.Add(model => model.Surname).Titled(Localizer[

问题 How should I construct Expression tree for string.IndexOf("substring", StringComparison.OrdinalIgnoreCase) ? I can get it working without the second argument: StringComparison.OrdinalIgnoreCase . These are my attempts so far: var methodCall = typeof (string).GetMethod("IndexOf", new[] {typeof (string)}); Expression[] parms = new Expression[]{right, Expression.Constant("StringComparison.OrdinalIgnoreCase", typeof (Enum))}; var exp = Expression.Call(left, methodCall, parms); return exp; Also

问题 I have the following extension method: public static string ToPropertyName<T,E>(this Expression<Func<E, T>> propertyExpression) { if (propertyExpression == null) return null; string propName; MemberExpression propRef = (propertyExpression.Body as MemberExpression); UnaryExpression propVal = null; // -- handle ref types if (propRef != null) propName = propRef.Member.Name; else { // -- handle value types propVal = propertyExpression.Body as UnaryExpression; if (propVal == null) throw new

问题 Using the following example i would like to use my Expression inside my Contains method, having it pass the query onto sql server using the EF . How can i build this up to work correctly? void Main() { IQueryable<Person> qry = GetQueryableItemsFromDB(); var filtered = qry.Filter(p=>p.CompanyId); } public static class Ext { public static IQueryable<T> Filter<T>(this IQueryable<T> items, Expression<Func<T, int>> resolveCompanyIdExpression) { IEnumerable<int> validComps =

问题 I just typed the following code: Expression<Func<ContentItem, bool>> expression = fileTypeGroupID.HasValue ? n => n.Document.MimeType.FileTypeGroupID == fileTypeGroupID.Value : n => true; Visual Studio is saying it can't infer the type of n . The code seems fine to me - it's just using a ternary operator to assign one of two Expression literals to an Expression variable. Is Visual Studio just not smart enough to infer the type of n inside a ternary operator, or have I made some kind of

问题 I am trying to create a generic Expression builder, which basically works fine as long as none the objects values is null. My current code looks like this (StartsWith as an example): case FilterOperationTypes.StartsWith: { ParameterExpression e = Expression.Parameter(typeof(T), "e"); PropertyInfo propertyInfo = typeof(T).GetProperty(field); MemberExpression m = Expression.MakeMemberAccess(e, propertyInfo); ConstantExpression c = Expression.Constant(val, typeof(string)); MethodInfo mi = typeof

问题 I have a SelectionCriteria class that I use for building Entity Framework query expressions, based on PredicateBuilder. Within its limits, it's working fine. I'd like to extend it so that it can query whether a field contains a substring. My problem is that I can't see how to build the needed expression object. My actual class supports and, or, and not, but they aren't relevant to my question. So I've simplified my example code to handle only a single binary operation: public class