Check to See What's Changed in Entity Framework

When you call Entity Framework's SaveChanges method, Entity Framework has to know what entities have changed in order to figure out what SQL Update/Delete/Insert statements to generate. If you also want to find out what entities have changed, then you can access that information through the DbContext object's ChangeTracker property.

Posted by Peter Vogel on 11/27/20180 comments

A Better Way to Test for Exceptions in Visual Studio

I've always argued that the only easier way to test your code than using Visual Studio Test is to not test at all. But that doesn't mean that I think Visual Studio Test is perfect.

For example, the ExpectedException attribute, when placed on a test method, lets you check to make sure that your code throws the appropriate exception when something goes horribly wrong. The problem with ExpectedException is that it applies to the whole test method, not just the "code under test." This means that if your test or production code throws that exception anywhere at all, the ExpectedException attribute will tell you that your test has passed. Unfortunately, that exception may or may not have been thrown where you actually expected it to be thrown. That's not quite what you want to test for.

Posted by Peter Vogel on 11/16/20180 comments

Making Breakpoints Useful in Visual Studio

How many times have you done this because you wanted to check how the value of some variable changes over time:

1. Set a breakpoint
2. Wait for Visual Studio to stop on the line
3. Check the value of the variables you're interested in
4. Press F5 to continue
5. Wait for Visual to stop on the line again
6. Check the value of the variables you're interested in
7. Press F5 to continue
8. Repeat ...

Posted by Peter Vogel on 11/13/20180 comments

Updating Request Messages in ASP.NET Handlers and Modules

In an earlier column I showed how to add custom processing to every request or response that your ASP.NET MVC or ASP.NET Web API site receives or produces. In that column, I offhandedly remarked about the kinds of things you can do to those incoming and outgoing requests. I didn't, however, actually provide the code (just as well, probably, because the column was getting into tl;dr territory). My conscience has caught up with me: Here's the kind of code you can put in a handler or module.

Posted by Peter Vogel on 11/05/20180 comments

Skipping Through Definitions and References in Visual Studio

In Visual Studio, if you want to find out what that xCt_1 variable really is or see the definition for that TranX class, the easiest way is to click on the variable or class name and press F12. You'll be taken straight to the statement that declares that variable or defines that class.

Posted by Peter Vogel on 10/29/20180 comments

Returning Status Codes from ASP.NET Core Controllers

Short, short tip: If you're working in an ASP.NET Core controller you may not have noticed that you have some new methods for generating a response to go back to the client: Ok, Created, NotFound and others. Each of these methods returns a standard HTTP status code. All these methods accept parameters that also let you pass in some content to be formatted into your return message's body.

Posted by Peter Vogel on 10/26/20180 comments

Leveraging and Testing Script Bundles with Content Delivery Networks

You can significantly reduce the time your users wait to see your ASP.NET pages by bundling your site's JavaScript files into a single zip file. You're not limited to downloading just your script files, however: There's nothing stopping you from including files from the Content Delivery Network of your choice. All you have to do is pass the URL to the CDN as the second parameter when you create a ScriptBundle, like this:

Posted by Peter Vogel on 10/25/20180 comments

Job Tip: Does the Future Belong to Xamarin.Forms?

I've written about managing your skills portfolio. That includes developing skills that are currently "niche" so that they may become your future "current" skillset -- and generate some lucrative jobs along the way. If you asked me now what I thought your next niche skillset should be I'd say Blazor ... but to do it through Xamarin.Forms. Here's why.

Posted by Peter Vogel on 10/17/20180 comments

Spell Check Your Comments in Visual Studio

While I’m opposed to writing comments in code, even I recognize the value of comments placed on a class or method declaration (I’m excluding properties because most don’t require commenting). Presumably, if you’re writing these comments it’s with the hope that someone will, someday, read them ... and it would be awfully embarrassing if you misspelled things in those comments.

Posted by Peter Vogel on 10/16/20180 comments

Speeding Up SQL Server: Planning for One-Time Queries

As I discussed in an earlier column, SQL Server keeps a plan cached for each query it sees (assuming the query requires planning in the first place, of course). That's great for speeding up processing the next time that query shows up because the plan for the query can simply be pulled from the cache.

Posted by Peter Vogel on 10/15/20180 comments

A Blazor Tip You Should Almost Certainly Ignore

In another column, I describe how you can, from JavaScript, call methods on C# objects defined in Blazor pages. As that sentence implies, however, there's no way to access properties on those objects ... at least, no official, documented way.

Posted by Peter Vogel on 10/10/20180 comments

Updating Entity Framework Objects with Changed Data

Assuming you're using the latest version of Entity Framework, the easiest way to update your database is to use DbContext's Entry class: It's just two lines of code no matter how many properties your object has.

As an example, here's some code that accepts an object holding updated Customer data, retrieves the corresponding Customer entity object from the database, and then gets the DbEntityEntry object for that Customer object:

Posted by Peter Vogel on 10/04/20180 comments