entity-framework

问题 I would like to create a function to retrieve a List of a given property name's Type. But i dont know yet how to create a working lambda selector. public IList<object> GetDistinctListOfProperty(string propertyName) { var propInfoByName = typeof(T).GetProperty(propertyName); if (propInfoByName == null) return new List<object>(); using (var db = new ApplicationDbContext()) { var lambda = //TODO return db.Set<T>().Select(lambda).Distinct().ToList(); } } 回答1: You can use this method to generate

问题 I am working with Entity Framework 6. I am working with 2 classes: public partial class StateProvince { public StateProvince() { Addresses = new HashSet<Address>(); } public int StateProvinceID { get; set; } public string StateProvinceCode { get; set; } public string CountryRegionCode { get; set; } public bool IsOnlyStateProvinceFlag { get; set; } public string Name { get; set; } public int TerritoryID { get; set; } public Guid rowguid { get; set; } public DateTime ModifiedDate { get; set; }

问题 What is the minimum set of database user permissions in SQL Server using Entity Framework database first approach in an ASP.NET MVC app? Is it only read and write or does EF need some more advanced permissions? 回答1: We typically use the following permissions Db Access admin, Db data reader And db data writer. These were sufficient in most cases. 来源： https://stackoverflow.com/questions/29052006/minimum-database-user-permissions-using-entity-framework-database-first-approach

问题 I am experimenting with custom naming convenctions in EF 6. I have 2 tables and one junction table (WebUser, UserRequest, WebUserUserRequest). I have written function that should be able to rename tables: from WebUser to web_user private string GetTableName(Type type) { var result = Regex.Replace(type.Name, ".[A-Z]", m => m.Value[0] + "_" + m.Value[1]); return result.ToLower(); } It is applied this way: modelBuilder.Types() .Configure(c => c.ToTable(GetTableName(c.ClrType))); The function is

问题 I am experimenting with custom naming convenctions in EF 6. I have 2 tables and one junction table (WebUser, UserRequest, WebUserUserRequest). I have written function that should be able to rename tables: from WebUser to web_user private string GetTableName(Type type) { var result = Regex.Replace(type.Name, ".[A-Z]", m => m.Value[0] + "_" + m.Value[1]); return result.ToLower(); } It is applied this way: modelBuilder.Types() .Configure(c => c.ToTable(GetTableName(c.ClrType))); The function is

问题 I am investigating the possibility to split one DB into multiple. We decided to move some tables into another database, but we have queries with join on these tables. I found a few solutions about how to achieve that: Azure SQL Database elastic query EXTERNAL DATA SOURCE But I don`t know what the difference between them and what to choose. Thanks for any help! 回答1: Azure SQL Database Elastic Queries and External data sources are two names for the same concept. My suggestion is to avoid cross

问题 When scaffolding a new ApiController with asynchronous actions and Entity Framework support in Visual Studio 2013, some methods wrap DbContext.SaveChangesAsync calls in try-catch blocks. For instance, the Put method, try { await db.SaveChangesAsync(); } catch (DbUpdateConcurrencyException) { if (!EmployeeExists(id)) { return NotFound(); } throw; } From msdn.microsoft.com about DbUpdateConcurrencyException , Exception thrown by DbContext when it was expected that SaveChanges for an entity

问题 When scaffolding a new ApiController with asynchronous actions and Entity Framework support in Visual Studio 2013, some methods wrap DbContext.SaveChangesAsync calls in try-catch blocks. For instance, the Put method, try { await db.SaveChangesAsync(); } catch (DbUpdateConcurrencyException) { if (!EmployeeExists(id)) { return NotFound(); } throw; } From msdn.microsoft.com about DbUpdateConcurrencyException , Exception thrown by DbContext when it was expected that SaveChanges for an entity

问题 Im using EF Core and Im trying to update a column/property of an entity. The column has a foreign key constraint...is nullable and is an int. The same table/entity has three or four other columns/properties the same datatype also foreign key constrained...and nullable When I update the values of any of these column using the Update command...It works perfectly fine...EXCEPT for one column. When I try to update that one column and i process the update it will save all changes...but that column

问题 In EF6 it was possible to define conventions based on property types during model building, like so... public interface IEntity { Guid Id { get; } } public class MyEntity : IEntity { public Guid Id { get; set; } } public class MyDbContext : DbContext { public override void OnModelCreating(DbModelBuilder builder) { builder .Properties<Guid>() .Where(x => x.Name == nameof(IEntity.Id) .Configure(a=>a.HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity)); } } This approach could also be