Special symbols
As mentioned earlier at the beginning of @, the character The string is free of escaping. Whatever is written in the string is what is written in the string. \ not escaped
?? Determine whether a value is null, if yes, it becomes the default value. If not, then the original value will be the same.
$ beginning string tampering and< code style="font-size: 0.85em; font-family: Consolas, Inconsolata, Courier, monospace; margin: 0px 0.15em; padding: 0px 0.3em; white-space: pre-wrap; border: 1px solid #eaeaea; background-color: #f8f8f8; border-radius: 3px; display: inline;">format has the same effect. For formatting strings, both regular and anonymous types are available. {} contains variable names or methods Or other expressions that can be converted into string
Square brackets written twice is to take the inner layer of square brackets and the content inside, no longer tampering. 
: format string for 
Format the time into the format you want
Special symbols
As mentioned earlier at the beginning of @, the string is free of escaping. Whatever is written in the string is what you encounter.< code style="font-size: 0.85em; font-family: Consolas, Inconsolata, Courier, monospace; margin: 0px 0.15em; padding: 0px 0.3em; white-space: pre-wrap; border: 1px solid #eaeaea; background-color: #f8f8f8; border-radius: 3px; display: inline;">\ not escaped
?? Determine whether a value is null, if yes, it will become the default value, if not, it will remain the original value
$ beginning string tampering and format has the same effect. Both regular and anonymous types can be used to format strings. {} contains variable names or methods or other expressions that can be converted into strings.
is written twice in square brackets Take the inner layer of square brackets and the content inside, and don’t tamper with it again. 
: format string for 
Format the time into the format you want
?