290 posts tagged with ".NET"

EF Core has three common ways to read one row: FirstOrDefaultAsync, SingleOrDefaultAsync and FindAsync. They look the same on a happy day and differ in what they send to MySQL and when they throw. This guide runs all three on the same row and compares the SQL, so you can pick with evidence.

With EF Core, you read rows by writing a LINQ query in C#, and EF Core turns it into SQL. The part that surprises people is timing: building the query sends nothing, and only ToListAsync or a similar call goes to MySQL. This guide reads rows with Where and OrderBy, shows the SQL each piece becomes, and proves the timing with real logs.

AddRange adds a list of new objects to the change tracker, and one SaveChangesAsync inserts them all. With Oracle's MySQL provider, EF Core packs the INSERT statements into one command to save round trips, and every object gets its own ID. This guide shows the code and the SQL it sends for 3 rows and for 50.

To insert a row with EF Core, add an object to its DbSet and call SaveChangesAsync. When that returns, the object's Id holds the number MySQL gave it, so you never have to query for it. This guide shows the two lines, the SQL they send, and how that new ID finds its way back.

ASP.NET Core can describe your API as an OpenAPI document, but that's a JSON file meant for tools. Scalar turns it into a page you can read and try in a browser. It takes one package and one line of code. This guide adds it to a .NET 10 C# Web API, for Development only.

A .http file is a plain text file that holds API requests. It lives next to your code and goes into Git with it, so everyone on the team has the same requests. VS Code with the free REST Client extension and Visual Studio both add a link above each request that sends it. This guide covers the format and how to send requests in each editor.

After I added one small GET endpoint, every request to my minimal API answered 500, health checks included. The log said Body was inferred but the method does not allow inferred body parameters. The endpoint took a record as a parameter, and ASP.NET Core assumes that comes from the JSON body, which GET doesn't get. [AsParameters] tells it to read the query string instead.

I wanted to read something from the database once, while the app started, so I asked app.Services for the DbContext in Program.cs. The app crashed: Cannot resolve scoped service 'Dewiride.Inventory.Data.InventoryDbContext' from root provider. Scoped services need a scope, and at startup there's no request to provide one. You can create one yourself in two lines.

My API refused to start: Cannot consume scoped service 'Microsoft.EntityFrameworkCore.DbContextOptions1[…InventoryDbContext]' from singleton 'Dewiride.Inventory.Api.CategoryCache'.A small cache class, registered as a singleton, asked for theDbContext. A singleton lives as long as the app, and a DbContextbelongs to one request, so ASP.NET Core stops it.IServiceScopeFactory` is the way for a singleton to use one.

A request with no price was accepted, and the product's price quietly became 0. No error, no warning. A C# decimal can't be null, so when the JSON leaves it out, it simply keeps its default value, and [Required] has nothing to complain about. Making the property decimal? fixes that.