Most efficient way to concatenate strings?

Question

What\'s the most efficient way to concatenate strings?

Answer 1

It's also important to point it out that you should use the + operator if you are concatenating string literals.

When you concatenate string literals or string constants by using the + operator, the compiler creates a single string. No run time concatenation occurs.

How to: Concatenate Multiple Strings (C# Programming Guide)

Answer 2

System.String is immutable. When we modify the value of a string variable then a new memory is allocated to the new value and the previous memory allocation released. System.StringBuilder was designed to have concept of a mutable string where a variety of operations can be performed without allocation separate memory location for the modified string.

Answer 3

It really depends on your usage pattern. A detailed benchmark between string.Join, string,Concat and string.Format can be found here: String.Format Isn't Suitable for Intensive Logging

(This is actually the same answer I gave to this question)

Answer 4

Try this 2 pieces of code and you will find the solution.

 static void Main(string[] args)
    {
        StringBuilder s = new StringBuilder();
        for (int i = 0; i < 10000000; i++)
        {
            s.Append( i.ToString());
        }
        Console.Write("End");
        Console.Read();
    }

Vs

static void Main(string[] args)
    {
        string s = "";
        for (int i = 0; i < 10000000; i++)
        {
            s += i.ToString();
        }
        Console.Write("End");
        Console.Read();
    }

You will find that 1st code will end really quick and the memory will be in a good amount.

The second code maybe the memory will be ok, but it will take longer... much longer. So if you have an application for a lot of users and you need speed, use the 1st. If you have an app for a short term one user app, maybe you can use both or the 2nd will be more "natural" for developers.

Cheers.

Answer 5

From this MSDN article:

There is some overhead associated with creating a StringBuilder object, both in time and memory. On a machine with fast memory, a StringBuilder becomes worthwhile if you're doing about five operations. As a rule of thumb, I would say 10 or more string operations is a justification for the overhead on any machine, even a slower one.

So if you trust MSDN go with StringBuilder if you have to do more than 10 strings operations/concatenations - otherwise simple string concat with '+' is fine.

Answer 6

If you're operating in a loop, StringBuilder is probably the way to go; it saves you the overhead of creating new strings regularly. In code that'll only run once, though, String.Concat is probably fine.

However, Rico Mariani (.NET optimization guru) made up a quiz in which he stated at the end that, in most cases, he recommends String.Format.