What is the best way to compare two strings to see how similar they are?

Examples:

My String
My String With Extra Words

Or

My String
My Slightly Different String

What I am looking for is to determine how similar the first and second string in each pair is. I would like to score the comparison and if the strings are similar enough, I would consider them a matching pair.

Is there a good way to do this in C#?

c# .net string algorithm string-comparison
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