EntityFramework.Exceptions 3.1.1 - Support for Entity Framework Core 3 and Improved API

In the previous article I introduced EntityFramework.Exceptions, a library which simplifies handling exceptions in Entity Framework Core but the library had one important limitation. In order to use it you had to inherit your custom DbContext from ExceptionProcessorContextBase class. This means that if you wanted to use some other base class for your DbContext you were out of luck. The latest version of the library solves this issue by

Introducing EntityFramework.Exceptions

When using Entity Framework Core for data access all database exceptions are wrapped in DbUpdateException. If you need to know whether the exception was caused by a unique constraint, value being too long or value missing for a required column you need to dig into the concrete DbException subclass instance and check the error number to determine the exact cause.

EntityFramework.Exceptions simplifies this by handling all the database specific details and throwing different exceptions for different cases. All you have to do is

Introducing LINQPad.QueryPlanVisualizer

If you are a heavy LINQPad user you have probably wished to be able to see query execution plan details inside LINQPad. Currently the only way to view query execution plan is to switch to SQL tab, click Analyze SQL button and open the query in SQL Server Management Studio. I got tired of clicking all these buttons and decided to write custom visualizer which solves the issue. With LINQPad.QueryPlanVisualizer you can now view query execution plan and missing indexes as well as create those missing indexes without leaving LINQPad.

Faking num lock, caps lock and scroll lock leds


Some time ago I came across a post where the author wanted to turn on and off num lock, cap lock and scroll lock led light without actually toggling their state. This sounded challenging and impossible but after some googling I found a piece of code in C for achieving exactly what I was looking for. In this post I show how it works and how to port it to C#

Building Expression Evaluator with Expression Trees in C# – Improving the Api

This post is part of a series about building a simple mathematical expression evaluator. For previous posts and full source code see Table of Contents.


In previous part we added support for variables but it has a big disadvantage: values of the variables are bound by position and not by name. This means that you should pass values for the variables in the same order as they appear in the expression. For example the following test will fail:

Using Reactive Extensions for Streaming Data from Database

You have probably heard about Reactive Extensions, a library from Microsoft that greatly simplifies working with asynchronous data streams and allows to query them with Linq operators. There are many different scenarios where using rx results in a much more simple and flexible code. This post demonstrates how to use reactive extensions for loading data from database asynchronously in chunks.

Building Expression Evaluator with Expression Trees in C# – Part 3


In part two of this series we built an expression evaluator capable of parsing expressions with parentheses. In this part we are going to add support for expression with variables.

Building Expression Evaluator with Expression Trees in C# – Part 2


In previous post I showed how to build a simple expression evaluator using expression trees. Although it works fine it has some drawbacks:

  • It does not support parentheses.
  • It does not support variables.
  • In some cases the result can be wrong as the parser is not using left to right parsing.
  • It is compiling delegates for every expression which results in slower execution.

To solve these issues we will use a different algorithm and deal with all points except variable support.

Building Expression Evaluator with Expression Trees in C# – Part 1


This is first part of a series about writing expression evaluator in C#. Even though there are several of them available already I decided to write my own as this one is based on expression trees and is very simple. The evaluator supports numeric expressions as well as expression with parameters.

Building Expression Evaluator with Expression Trees in C# – Table of Contents

This is table of contents for Building Expression Evaluator with Expression Trees in C# series. We are going to build a simple mathematical expression evaluator in C# using expression trees. The library supports simple expressions such as 2.5+5.9, 17.89-2.47+7.16, 5/2/2+1.5*3+4.58, expressions with parentheses (((9-6/2)*2-4)/2-6-1)/(2+24/(2+4)) and expressions with variables: var a = 6; var b = 4.32m; var c = 24.15m; Assert.That(engine.Evaluate("(((9-a/2)*2-b)/2-a-1)/(2+c/(2+4))", a, b, c), Is.EqualTo((((9 - a / 2) * 2 - b) / 2 - a - 1) / (2 + c / (2 + 4)))); At the end of the series full source code will be available at github and the library will be published to NuGet.