Difference between concatenation and {} [duplicate]

Question

This question already has answers here:

String output: format or concat in C#? (32 answers)

Concatenate multiple strings versus String.Format [duplicate] (2 answers)

Closed 9 years ago.

I am wondering what the difference is if I put

Both refer to string foo = "world";

 Console.WriteLine("Hello" + foo); //Concatenation 

and

 Console.WriteLine("Hello {0}", foo); //Whatever this is called (still a beginner guys)

Answer 1

both look similar as you use string types. suppose you deal with different types. Then you will see the difference between Concatenation and Composite Formatting.

 int myInt = 2;
 Console.WriteLine("This is my int {0}", myInt);

Suppose now you want to put more types inside the composite formatting:

 char  myChar = 'c';
 bool myBool = true;

 Console.WriteLine("This is my bool {0} and myChar {1}", myBool ,myChar );

But Concatenation is the process of appending one string to the end of another string. When you concatenate string literals or string constants by using the + operator, the compiler creates a single string. No run time concatenation occurs. However, string variables can be concatenated only at run time. In this case, you should understand the performance implications of the various approaches.

Answer 2

Concatenation simply puts two strings together. This is an extremely common practice found in just about every programming language.

Your second example is called string formatting. This gives you a lot of control of how the string will look when it's displayed, depending on what language or framework you're using.

Here's a great link to an explanation of string formatting. It uses string.Format() instead of the console but the concept still applies.

Answer 3

The second option allows you to do more complex formatting. With a string, there is little advantage, but if you were using a double value, for example, you could use the composite format options to specify the amount of precision to display or other options.

Answer 4

This is a type of string formatting.

What Console.Write is doing is the equivalent of this:

String.Format("Hello {0}. I am {1} years old.", PersonName, PersonAge);

It just concatentates the string in an easier to understand way, as compared to:

"Hello " + PersonName + ". I am " + PersonAge + " years old.";