@ Usage in C # string

1. The String constant in C # can start with @. This advantage is that the escape sequence "not" is processed and output as "is,
That is to say, we can easily coding without adding escape characters. For example
String filePath = @ "c: DocsSourcea.txt"; // rather than "c: DocsSourcea.txt"
 
2. To include a double quotation mark in a string caused by @, two pairs of double quotation marks are required.
At this time, you cannot use the escape quotes, because the escape usage here has been blocked. For example
@ "Ahoy! "" Cried the captain. "; // the output is:" Ahoy! "Cried the captain.
It is a bit like the single quotation mark constant Processing Method in SQL:
DECLARE @ msg varchar (100)
SET @ msg = ''Ahoy! ''Cried the captain. '-- the output is: 'ahoy! 'Cried the captain.

3. @ Recognizes line breaks
In fact, I don't know how to describe this feature. I just accidentally discovered it. Let's take a look at the following code:
String script = @"
<Script type = "" type/javascript "">
Function doSomething ()
{
}
</Script> ";

Write js in the cs file, and the structure is very clear. Normally we are coding like this:
String script2 = "<script type =" type/javascript "> function doSomething () {}</script> ";
// Or
String script3 =
"<Script type =" type/javascript ">" +
"Function doSomething () {" +
"} </Script> ";
We usually select the latter because the js Code is generally long, the method body is large, or other variables need to be connected, so that the structure is clearer.
Note: If the number of "splices" is large, you should consider using StringBuilder to improve performance.
It is also common to splice SQL statements in a program, such
Private const string SQL _INS_USER = @"
Insert into t_User ([UserName], [Password], Email)
VALUES (@ UserName, @ Password, @ Email )";
 
However, we need to pay attention to the following question: String Length
See the following test code:
Private const string SQL _INS_USER1 = @"
Insert into t_User ([UserName], [Password], Email)
VALUES (@ UserName, @ Password, @ Email )";
Private const string SQL _INS_USER2 = @ "INSERT INTO t_User ([UserName], [Password], Email)
VALUES (@ UserName, @ Password, @ Email )";

Private const string SQL _INS_USER3 = @ "INSERT INTO t_User ([UserName], [Password], Email)
VALUES (@ UserName, @ Password, @ Email )";

Static void Main (string [] args)
{
Console. WriteLine (SQL _INS_USER1.Length); // 126
Console. WriteLine (SQL _INS_USER2.Length); // 112
Console. WriteLine (SQL _INS_USER3.Length); // 86
}
We can see that the lengths of the three strings are different, 14 = 126-112 and 26 = 112-86. In the code editor, SQL _INS_USER1
After the first line break in, 13 spaces are indented (before INSERT), while
After the first line break in SQL _INS_USER2, 25 spaces are indented (before VALUES ),
Then, add a line break, just 14 and 26