C#

C# Programming Language

C# – Remove a set of characters from a string

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The fastest and simplest way to remove a set of characters from a string is to use StringBuilder + List<char>, like this: I compared this with three other approaches. I did 100,000 iterations with a string with 2500 characters and a list of 15 characters to remove. This StringBuilder approach is almost 2x faster than … Read more

C# – Convert a list of strings into a set of enums

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Let’s say you have a list of HTTP status codes that you read in when the service starts up (perhaps from appsettings.json or from the database). Whenever you send an HTTP request, you want to check if the returned status code is in this list of status code. To make things more efficient, you want … Read more

C# – Get list of assemblies currently loaded and output metadata

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You can get all of the loaded assemblies and output their metadata like this: This outputs the following information: In the rest of this article, I’ll show how to get custom attributes (such as which build config was used – Debug or Release), how to add your own custom metadata, how to check if it’s … Read more

EF Core – Aggregate SELECT queries

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In this article, I’ll show how to use EF Core to aggregate data for the whole table, per group, and how to only include groups that meet a condition. I’ll show three different aggregates – count, sum, and average. In each scenario, I’ll show the LINQ query, the SQL query it generated, and the results … Read more

EF Core – SELECT queries involving multiple tables

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When you have tables that are related, you’ll often need to get data from both tables at once, or filter records from one table based on values in another table. In this article, I’ll show examples of executing queries like this where more than one table is involved. You can do most queries using LINQ. … Read more

EF Core – Basic SELECT queries

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In this article, I’ll show examples of how to execute basic SELECT queries when using EF Core. You can execute queries using LINQ or by writing raw SQL. I’ll use SQL Profiler to show the queries generated by LINQ. Note: I’ll be using .AsNoTracking().ToListAsync() in all cases. You’ll need to decide if that’s the right … Read more

EF Core – How to add a computed column

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To add a computed column in EF Core, override DbContext.OnModelCreating() and specify the computed column using ModelBuilder, like this: In this article, I’ll show a full example of adding a computed column and then show how to specify that the computed column should be persisted. Example of adding a computed column Let’s say we have … Read more

EF Core – How to create a composite primary key

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A composite primary key is a primary key that contains more than one column. In EF Core, to create a primary key with one column, you would use the [Key] attribute. To create a composite primary key with multiple columns, you have to override DbContext.OnModelCreating() and then specify all of the columns included in the … Read more

EF Core – How to add indexes

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In this article, I’ll show how to add indexes using EF Core. If you’re not sure about why you would need indexes, take a look at this article explaining how indexes greatly improve query performance. Add an index with a single column The simplest way to add an index is to by adding the [Index] … Read more

EF Core – Add a foreign key

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In this article, I’ll show how to add a foreign key using EF Core. Then I’ll show how foreign keys affect inserts and deletes. How to add a foreign key A Show has one or more Episodes. In this section, I’ll show how to link these two tables together to enforce the 1-to-many relationship. In … Read more