C# 中的 Regex 模式用于 C# 中的 Regex.Replace()

Question

I have a string

string str1 = "SELECT * FROM A INNER JOIN B JOIN C JOIN A INNER JOIN B LEFT JOIN C";

I want to Replace the JOIN not followed by INNER , LEFT etc with \\nJOIN

My desired output is

SELECT * FROM A INNER JOIN B \nJOIN C \nJOIN A INNER JOIN B LEFT JOIN C 

I am a novice C# programmer and what I wanted to use is

var pattern = NOT IN("INNER" || "OUTER" || "LEFT") + @"\b"+ "JOIN";
var output = Regex.Replace(str1, pattern, "\nJOIN", RegexOptions.IgnoreCase); 

Here I stuck with implementing the NOT IN("INNER" || "OUTER" || "LEFT") with RegEx.

Can you please help me in this regard. Thanks in advance.

Answer 1

I think this is what you're looking for:

string str1 = "SELECT * FROM A INNER JOIN B JOIN C JOIN A INNER JOIN B LEFT JOIN C";
string result = Regex.Replace(str1, @"(?<!INNER)\s+JOIN", "\nJOIN");
//result: SELECT * FROM A INNER JOIN B \nJOIN C \nJOIN A INNER JOIN B LEFT \nJOIN C

I used this handy website to learn how to do it: regex101

Remember to use the quick reference search in the lower right to find the character or expression you need (eg I searched "Not" in your case)

UPDATED: to make it more robust and allow 1 to n amount of blank spaces between INNER and JOIN