Reverse engineer a database with AspNetCore in Visual Studio

For some reason the .NETCore designers did not think, that developers want to follow best practices by separating the data layer from the presentation layer. The Entity framework out of the box only works if the database is accessed from the main application project. When we try to reverse engineer a PostgreSQL database from a […]

Procedure or function ‘`…_Insert`’ cannot be found in database …

When you use the Microsoft .NET Entity framework to access a MySql database, the autogenerated code throws an error when you try to insert a row into the database with context.MY_TABLE.Add(MY_OBJECT); Server Error in ‘/’ Application. Procedure or function ‘`…_Insert`’ cannot be found in database ‘`…`’. Description: An unhandled exception occurred during the execution of […]

No connection string named ‘…’ could be found in the application config file.

Two-tier applications separate the presentation layer and the data layer, and all database access related objects are located in the data-tier. When the application runs, the config file of the main project is read. In web applications, it is the web.config, in console applications the app.config file. When you get the following runtime exception Exception thrown: ‘System.InvalidOperationException’ in […]

The given assembly name or codebase was invalid. (Exception from HRESULT: 0x80131047)

When I made changes to the web.config file of an ASP.Net C# application, I have accidentally deleted a comma, and I started to get the runtime error message: The given assembly name or codebase was invalid. (Exception from HRESULT: 0x80131047) Make sure all necessary commas are there in the config files, Visual Studio does not […]

Generate Entity Framework Entity Data Model in Visual Studio 2017

Visual Studio 2017 has many project type options, and not all of them support the Entity Framework user interface to generate the Entity Framework Data Model (EDMX) file. If you create an ASP.NET Web Application(.NET Framework) you can add the EDMX file to it. The .NET Core projects do not support the Entity Framework Data Model […]

{“error”:”Entity type ‘AspNetUserRoles’ has composite primary key defined with data annotations. To set composite primary key, use fluent API.”}

When a database table has composite keys (multiple columns are in the key) you cannot use the usual key definition [Key] [Display(Name = “UserId”)] public string UserId { get; set; } [Key] [Display(Name = “RoleId”)] public string RoleId { get; set; } When you run the application you get the error message: {“error”:”Entity type ‘AspNetUserRoles’ has composite […]

Generate SQL script from Entity Framework migration script

It is not recommended to execute Entity Framework migration scripts in production, It is important that you execute all SQL steps manually on the production database section-by-section to immediately see the result and be able to recover in case a destructive action goes wrong. The Visual Studio .NET application templates contain Entity Framework migration scripts to […]

DbUpdateConcurrencyException: Database operation expected to affect 1 row(s) but actually affected 0 row(s). Data may have been modified or deleted since entities were loaded.

The .NET Core Entity framework makes database access easy. When you auto-generate a Razor page in a .NET web application to edit a data row, the scaffolding places controls on the page for every column. There are columns in most of the tables that we don’t want to display or edit, like keys, checksums, password […]

No mapping specified for instances of the EntitySet and AssociationSet in the EntityContainer

When you move your Visual Studio solution to another workstation you may encounter the following error message: System.Data.Entity.Core.MappingException was unhandled by user code HResult=-2146232032 Message=Schema specified is not valid. Errors: : error 2062: No mapping specified for instances of the EntitySet and AssociationSet in the EntityContainer … Source=EntityFramework   In this case it may help if […]

No Entity Framework provider found for the ADO.NET provider with invariant name ‘System.Data.SqlClient’

When one of the projects in your solution is referencing the Entity Framework to access a database the Entity Framework NuGet package is added to that project. In the Visual Studio IDE your application may work fine, but when you deploy it to the test or production server the following error message may appear: Exception […]