I just came across an, erm interesting issue when exporting some data to a CSV file. When I tried to open the file in Excel, I got the rather helpful error message “The file format and extension of ‘filename.csv’ don’t match. The file could be corrupted or unsafe. Unless you trust its source, don’t open it. Do you want to open it anyway?” If you click the Yes button, then you get the even more helpful error message “Excel has detected that ‘filename.csv’ is a SYLK file, but cannot load it. Either the file has errors or it is not a SYLK file format. Click OK to try to open the file in a different format.” At this point, you go and look to see if there are any jobs going on the cashiers at Tesco! Turns out that the fix is very simple. If you export an ID field…
Dot Net What Not Posts
I kept having problems when I opened a XAML file, in that the designer would show the following… This makes it somewhat hard to design a view when you can’t see the design! It turns out that when the XAML designer loads, it attempts to run code in your view model. There is some (questionable) justification for this, but overall, it’s a huge pain, and is one of the reasons why editing XAML files can be such a slow and tedious process. However, there is a way to mitigate the problem. If you can identify which parts of your code are causing issues, you can add code to prevent them from running when you are in Visual Studio. First you need to add the following line to the top of your code file… …then wrap the offending code in a check as follows… Apart from the fab method name (who…
We have found a problem whereby when a window loads, some of the buttons are disabled. Clicking anywhere on the window (even on the title bar) enables the button, but this doesn’t give a good user experience. Thankfully the fix is simple. You need to find a place in the view model code where all the data has loaded, all events have been raised, and all INC properties have been set. Then you add the following lines… That will fix the issue. Ideally you would do this in the base view model, but this requires having somewhere in there where you know all data has been loaded. If you have that, then consider yourself amongst the blessed
I recently came across a situation where I needed to delete all the data from a table and reinsert it (don’t ask why, it was quite sensible actually). I wanted to avoid anyone reading from the table while it was in an intermediate state, ie with part of the data in and part not. I did a quick search on using transactions in EF, and came across an article (not linked for reasons that should become apparent) that strongly recommended not using them at all. This all seemed sensible advice, until I read the comments. A lot of people criticised the article as giving very bad advice. Amongst the links was one to an MSDN page that explained how to use transactions with EF6 onwards. This was much cleaner than the advice in the previous article, and being from Microsoft, one hopes it is more authoritative. It’s worth reading the whole…
I’ve recently discovered a very useful property that’s been available since .NET 4.5, called Delay. It’s used in the XAML when binding a property, and it delays sending the binding back to the ViewModel for the number of milliseconds that you specify. For example… In this example, the SearchText property will not get updated as soon as the user types, but rather will wait 1 second from when the user finishes typing to update the property. This is beneficial when you have a service call, or search method that is triggered when the bound property is changed. Here are two links that describe the usage and functionality very well: http://www.jonathanantoine.com/2011/09/21/wpf-4-5-part-4-the-new-bindings-delay-property https://msdn.microsoft.com/en-us/library/system.windows.data.bindingbase.delay(v=vs.110).aspx#Version%20Information
OK, so hands up who knows the difference? Hmm, just as I thought, not many. Don’t worry about it, nor did I until just now! Rather than rambling on (as usual), I’ll just point you at a StackOverflow question where this was answered as clearly as this is likely to be answered anywhere! http://stackoverflow.com/questions/2876616/returning-ienumerablet-vs-iqueryablet By the way, if you just query your EF context and don’t explicitly convert your results, you’ll end up with an IQueryable<T>. If you use .AsEnumerable(), you’ll end up with an IEnumerable<T> (surprisingly enough).
You have probably noticed that Visual Studio can sometimes take an age to load a XAML file. The reason for this is because it runs any code it can find before displaying the designer. This can take a while. Sometimes, you might see something like this… This happens when Visual Studio encounters an unhandled exception in the code it’s running while trying to load the XAML file. This is, to say the least, somewhat annoying. You may be tempted to click the middle link that offers to disable running project code in the designer. Don’t. Trust me, you don’t want to go there. Really, I’ve done it, and it took me about an hour to get the designer back into a workable state. Whilst this sounds like a good idea in theory, in practice it has all sorts of side-effects that you probably didn’t consider. For example, if you use…
One annoying problem is when sometimes you try to build your solution, only to get a pile of compilation errors due to a missing DLL. This is often caused by one of the DLLs not downloading from NuGet. The package will be in packages.config, but only the .pdb file gets downloaded.
Even more annoying is when you’re the only developer to have this problem. Everyone else can build the solution without problem.
The answer is fairly simple, but not obvious. Read more for the details.
It seems we aren’t the only ones to find filtering and sorting child entity collections unnecessarily painful. Someone has been kind enough to write a Nuget package (part of a suite of them by the looks of things) that simplifies your code significantly.
This package removes the need for some of the tortuous hoops we had to negotiate before.
A fairly standard set up for me is to have a solution in which I have a Data project that contains an EF6 .edmx file, generated from an existing database. I then split the entities into a separate Entities project, and have a Repositories project that references them both.
The problem was, I wanted to write unit tests against the code, but couldn’t work out how to do it. This post shows what didn’t work, and then what did.
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