What s with the dollar sign string

Question

I have been running through some C  exercises in a book  and I ran across and example that stumped me  Straight from the book  the output line shows as   Console WriteLine    n tYour result is  result        Now I as if stands  the code works and the double result shows as expected  However  not understanding why the   is there at the front of the string  I decided to remove it  and now the code outputs the name of the array  result  instead of the contents  The book doesn t explain why the   is there  unfortunately   I have been scouring the VB 2015 help and Google  regarding string formatting and Console WriteLine overload methods  I am not seeing anything that explains why it is what it is  Any advice would be appreciated

User · Answer

String Interpolation

is a concept that languages like Perl have had for quite a while, and now we’ll get this ability in C# as well. In String Interpolation, we simply prefix the string with a $ (much like we use the @ for verbatim strings). Then, we simply surround the expressions we want to interpolate with curly braces (i.e. { and }):

It looks a lot like the String.Format() placeholders, but instead of an index, it is the expression itself inside the curly braces. In fact, it shouldn’t be a surprise that it looks like String.Format() because that’s really all it is – syntactical sugar that the compiler treats like String.Format() behind the scenes.

A great part is, the compiler now maintains the placeholders for you so you don’t have to worry about indexing the right argument because you simply place it right there in the string.

C# string interpolation is a method of concatenating,formatting and manipulating strings. This feature was introduced in C# 6.0. Using string interpolation, we can use objects and expressions as a part of the string interpolation operation.

Syntax of string interpolation starts with a ‘$’ symbol and expressions are defined within a bracket {} using the following syntax.

{<interpolatedExpression>[,<alignment>][:<formatString>]}

Where:

interpolatedExpression - The expression that produces a result to be formatted
alignment - The constant expression whose value defines the minimum number of characters in the string representation of the result of the interpolated expression. If positive, the string representation is right-aligned; if negative, it's left-aligned.
formatString - A format string that is supported by the type of the expression result.

The following code example concatenates a string where an object, author as a part of the string interpolation.

string author = "Mohit";  
string hello = $"Hello {author} !";  
Console.WriteLine(hello);  // Hello Mohit !

Read more on C#/.NET Little Wonders: String Interpolation in C# 6

User · Answer

It s the new feature in C  6 called Interpolated Strings   The easiest way to understand it is  an interpolated string expression creates a string by replacing the contained expressions with the ToString representations of the expressions  results   For more details about this  please take a look at MSDN   Now  think a little bit more about it  Why this feature is great   For example  you have class Point   public class Point       public int X   get  set         public int Y   get  set        Create 2 instances   var p1   new Point   X   5  Y   10    var p2   new Point   X   7  Y   3      Now  you want to output it to the screen  The 2 ways that you usually use   Console WriteLine  The area of interest is bounded by      p1 X         p1 Y      and      p2 X         p2 Y           As you can see  concatenating string like this makes the code hard to read and error-prone  You may use string Format   to make it nicer   Console WriteLine string Format  The area of interest is bounded by  0   1   and   2   3     p1 X  p1 Y  p2 X  p2 Y      This creates a new problem    You have to maintain the number of arguments and index yourself  If the number of arguments and index are not the same  it will generate a runtime error    For those reasons  we should use new feature   Console WriteLine   The area of interest is bounded by   p1 X   p1 Y   and   p2 X   p2 Y        The compiler now maintains the placeholders for you so you don   t have to worry about indexing the right argument because you simply place it right there in the string   For the full post  please read this blog

[c#] What's with the dollar sign ($"string")

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