Strings, Part I

Enough with numbers for a while. Strings of characters are another important type in C#.

A string in C# is a sequence of characters. For C# to recognize a literal sequence of characters, like hello, as a string, it must be enclosed in quotes " to delimit the string: "hello". Special cases are considered later in String Special Cases.

String Concatenation

Because everything in C# is typed, C# can give a special meaning to operators depending on the types involved, as we saw with /. We can operate on numbers with arithmetic operators, including +. With strings + has a completely different meaning. Look at the example in csharp:

csharp> "never" + "ending";

The plus operation with strings means concatenate the strings: join them together end to end.

C# is even a bit smarter. If you use a + with a string, presumable you are looking to produce a string, so even if the second operand to the + is not a string, it is automatically converted to a string representation before concatenating:

csharp> int x = 42;
csharp> string result;
csharp> result = "We get " + x;
csharp> result;
"We get 42"

You can chain concatenations. We could make a full sentence adding a period:

csharp> "We get " + x + ".";
"We get 42."

Note to Python programmers: Unfortunately there is no * multiplication operator for strings in C#.

Four Copies Exercise

In csharp declare and initialize a string variable. Write an expression that evaluates to four copies of the string, so it works no matter what value you gave your string.

Sum String Exercise

In csharp declare and initialize two int’s, x and y. Then enter an expression whose value is “x + y is 56”, except that 56 is replaced by the sum of x and y, and is not a literal, but calculated from the actual values of variables x and y (which do not need to add up to 56 specifically).

This has a trick to it.

Ints and Strings Added

In csharp enter

int x = 2;
int y = 3;

Think what the csharp response is to each of these then write one predicted response at a time, then test it, and put the right answer beside your answer if you were wrong:

x + "??" + y;
x + y + "??";
(x * y + "??");
"??" + x * y;
"??" + x + y;
x + "??" * y;

Can you explain the ones you got wrong, after looking at the actual answer? Precedence and operation order is important.