entity-framework

问题 I'm developing an Entity Framework Code First (v. 4.4.0.0) C# library with .Net Framework 4.0. I don't know how to set zero-to-one relationship. My model is the following: A Talk can be created by only one user ( StarterUserId ). A Talk can have only one recipient user ( RecepientUserId ) or only one group ( RecipientGroupId ). Note : That means that RecepientUserId is null if RecipientGroupId is not null; or RecepientUserId is not null if RecipientGroupId is null. A user can be a recipient

问题 I am using Entity Framework in a C# application and I am using Lazy Loading. We noticed one query has an extremely high impact on our CPU, which merely calculates a sum. When debugging the query generated by Entity Framework it creates a INNER JOIN (SELECT ... which is not performant. When I manually change the query to a proper JOIN the query time goes from 1.3 sec to 0.03 sec. Let me illustrate it with a simplified version of my code. public decimal GetPortfolioValue(Guid portfolioId) { var

问题 I am trying to get a row from a table using the entity framework in C#. I have a table called "TipoPlanta" with a primary key called "Tipo" which is of type String. When I try to get a row from the table usng a String I can only find something if I use a string literal. If I use the string passed to the method I find no rows. I have the following method which has a bit of added stuff that I have been trying to debug. I pass the String tipoString which in this example has a value of "Arbol

问题 I am trying to get a row from a table using the entity framework in C#. I have a table called "TipoPlanta" with a primary key called "Tipo" which is of type String. When I try to get a row from the table usng a String I can only find something if I use a string literal. If I use the string passed to the method I find no rows. I have the following method which has a bit of added stuff that I have been trying to debug. I pass the String tipoString which in this example has a value of "Arbol

问题 I can't find examples on how to use EF Database Initializers with EF Core nor can I find a list of EF Database Initializers shipping with EF Core. Has the concept of Database Initializers become obsolete? What's the current approach of initializing a database ... or not initializing an existing database? 回答1: In .Net core you can use functions of Database property form DbContext instance. It allows you to create database (EnsureCreated), destroy database (EnsureDeleted) and migrate to last

问题 In my project we have a branch model that has a separate development branch and has a separate branch for each release. It may look like this: dev ______ ______ / \ / \ master --+---+----+---+---+----+----+--- (...) r1 \______/ r2 \_______/ So we develop on dev merge it to master and then we create a release branch (r1, r2, ...). We want to use EF 6 (manual not automatic) migrations but we have a question that we don't know how to answer. Imagine this: dev _(1)__ ____(4) / \ / \ master --+---

问题 In my project we have a branch model that has a separate development branch and has a separate branch for each release. It may look like this: dev ______ ______ / \ / \ master --+---+----+---+---+----+----+--- (...) r1 \______/ r2 \_______/ So we develop on dev merge it to master and then we create a release branch (r1, r2, ...). We want to use EF 6 (manual not automatic) migrations but we have a question that we don't know how to answer. Imagine this: dev _(1)__ ____(4) / \ / \ master --+---

问题 I have a new project created using Visual Studio 2013 with an ADO.NET Entity Data Model (EF6). Now I have to use some Dynamic Data function (like access to MetaTable object), so I add this code: MetaModel model = new MetaModel(); model.RegisterContext(() => { return ((System.Data.Entity.Infrastructure.IObjectContextAdapter)new KiwiJuiceEntities()).ObjectContext; }, new ContextConfiguration() { ScaffoldAllTables = true }); but I've got this error: Type of context 'System.Data.Entity.Core

问题 I have a new project created using Visual Studio 2013 with an ADO.NET Entity Data Model (EF6). Now I have to use some Dynamic Data function (like access to MetaTable object), so I add this code: MetaModel model = new MetaModel(); model.RegisterContext(() => { return ((System.Data.Entity.Infrastructure.IObjectContextAdapter)new KiwiJuiceEntities()).ObjectContext; }, new ContextConfiguration() { ScaffoldAllTables = true }); but I've got this error: Type of context 'System.Data.Entity.Core

问题 I have a project that has 4 entity data model.for building them I don't want save a connection string in my project and I want store a connection string in app.config files and share it between my models.How I can do this? thanks 回答1: Assuming DbContext and model/database first. Leave the generated EF connection strings in your app.config file intact. As Arthur said, they contain the paths to the EF metadata (csdl/ssdl/msl). They are also used during development by the model designer. Add a