It is common to need to append one string to another in C# programs. This is called concatenation. In languages where strings can be modified after being created, this is efficient—but in C#, strings are immutable and concatenation leads to a new string creation.

Creating too many new strings will cause excessive allocations and copying of memory. This can lead to big performance problems. StringBuilder can eliminate this problem by providing a buffer into which all the strings are copied, with fewer allocations.

We can use StringBuilder when:

In the case of two strings, it can be faster just to concatenate the strings directly, but it is also acceptable to use StringBuilder. If further appends are needed, the StringBuilder will prevent future performance problems. So it is useful as a preventative measure against excess string copies.

I do not know everything about every computer language, or even every one I write about on this site. Instead, I learn as I go along. From other languages like C# I was familiar with the concept of enums—types that store known values and can be referenced by name.

But in Rust, enums have an additional feature—they are an algebraic data type. This means a value in an enum can reference some data—like a struct instance, a String, a tuple or a number.

In practice, this means we can use a single enum to refer to multiple data types:

So we can create a Color, and it could have a value of Red with a String, or a value of Blue with a usize instead. And we can refer the Color as meaning either Red or Blue—and a String or usize only in appropriate cases. This can simplify some programs where we must return many types of data from a single function.

There are many articles about Windows Forms and WPF on this site—and they have been helpful to people for a long time. With Windows Forms and WPF developers can make Windows applications that have windows, buttons, dialog boxes, and C# or VB.NET code.

But as competing technologies like web browsers have become more powerful and widespread, Windows Forms and WPF have become less useful. It is possible to build a simple web server in nearly any language that serves HTML pages and handles input from clicks and POST requests. And web browsers have many advantages over WinForms and WPF:

For some applications that need native speed, like text editors, web browsers and even games, it is necessary to use native UI controls. But for the vast majority of applications that one might need, web browsers are probably a better platform to target. Of course, for older applications that have already been written, continuing to support Windows Forms and WPF is necessary.

Suppose you are writing a Rust program, and you are having problems with the borrow checker. The compiler is giving you messages about "use of moved value" and "cannot borrow data as mutable." Should you give up?

No, you should not give up. Instead, here are some tips for dealing with the borrow checker.

Basically in Rust it helps to know what struct owns all the memory in a program. Then you don't have to worry about the memory anymore—you can just access the data by index, referencing the owner struct. In this approach, most structs do not need to store references to other structs.

When we write code in a language like C#, Java, Python or Rust we often have to choose between arrays or lists and hash tables. An array or list stores elements one after another. A hash or dictionary stores elements in locations that are based on the values of the elements themselves (hash codes).

Often we can realize a performance improvement in programs by using hashed collections correctly. If our program loops over an array to find an element by value, it is likely faster to use a hash table instead.

Here are some signs it is worth trying a dictionary:

If a program needs the packed elements in a linear collection, arrays or lists are a better choice. They are more memory-efficient and faster to loop over. But if the program has excessive searching by value, a hash collection is probably an improvement.

2D arrays are a common topic that people want to know about. How can you make a 2D array in C#, Python, Java, Go—what is the syntax, how can you access elements? But for the most part the articles I have on 2D arrays ignores the main problems with 2D arrays.

Basically the best time to use a 2D array is never. It is usually better to just use one-dimensional arrays, nested arrays (which are like jagged arrays), or even hashtables. Often, data are sparse, and 2D arrays in most languages use memory for all elements—this wastes a lot of memory.

Here are some things I have found:

2D arrays, like recursive methods, are a feature that most programs would be better off not using. Other solutions are simpler and usually faster. I suppose, for completeness, learning about 2D arrays is worthwhile however.

Some years ago I had a C# program that was taking too long to finish. The time required for it to finish processing was approaching a minute. For an interactive program, this was not acceptable, so I focused on optimizing the program.

Eventually I added multi-threading to the program, and it finished in less than 100 milliseconds. However, I was still curious as to whether other languages, like Go or Rust, could be faster than C#.

I ported the program to Go, and although I changed the algorithms a bit to be more efficient (this often happens when porting) the program was at least 20% faster, even without any optimization-specific work. The Go program took 80 milliseconds to finish.

Finally, I ported the Go program to Rust, and surprisingly this version was not only plagued with fewer bugs (it worked correctly right away), but it also was twice as fast as the Go version, at 40 milliseconds.

In the comparison of C#, Go and Rust, I found that C# and Go were similar, although Go was faster for command-line programs as it was compiled ahead-of-time. Rust meanwhile was the fastest programming language to use, and this was before any optimization work was done—it was just the first compiling version.

Even though it is used for many programs, VB.NET is mostly ignored even by its creators. Other languages like C# get much more attention; new features are often exclusive to C# in .NET updates.

But VB.NET persists, and I have found it has some good points—even features that C# does not have. One thing it does, for example is support case-insensitive syntax. So we can use sub in place of Sub for a subroutine.

This is helpful for VB.NET for these reasons:

It is a good compromise to just leave the syntax case-insensitive. This can also speed up development if you have a capitalization inconsistency but the program still compiles correctly. Case-insensitive syntax is a useful feature for VB.NET.

In the past I spent a significant amount of time working on large C# projects with many files. The C# language can be verbose and require excess time to create new classes—particularly several years ago.

One newer feature in C# that I feel can make developing large, multi-file programs easier is the "global using" directive. While using as a directive only applies to the current file, global using applies globally to all files in the project.

So each file that you create—like a new class file—you can omit the commonly-needed using directives. In many projects, a single directive is used in many places—like the System namespace for programs that write to the console, or System.Text for programs that use StringBuilder. I feel global using directives are a valuable time-saving (and file-size-saving) feature in this language.

For the most part, Go is a language where things are done in an obvious way. Slices, for example, are done on units of the original type, like elements in an array. But taking substrings is somewhat more complicated.

In Go, strings can be thought of as collections of bytes, and collections of characters (or runes). This is because some Unicode characters (like those with accents) have more than one byte. But ASCII strings have just one byte per character.

The Go substring article is one of my most useful:

Substrings in Go are done a little differently than in other languages like C#, but the idea of using slices for substrings makes sense. Writing the Go substring article helped me figure out this important aspect of Go.