Auto quotes around string in c# - build in method?

string quotedString = string.Format("\"{0}\"", originalString);

Yes, using concatenation and escaped characters

myString = "\"" + myString + "\"";

Maybe an extension method

public static string Quoted(this string str)
{
    return "\"" + str + "\"";
}

Usage:

var s = "Hello World"
Console.WriteLine(s.Quoted())

There is no such built in method to do your requirement

There is SplitQuotes method that does something Input - This is a "very long" string Output - This, is, a, very long, string

When you get a string from textbox or some control it comes with quotes.

If still you want to place quotes then you can use this kind of method

private string PlaceQuotes(string str, int startPosition, int lastPosition)
{
    string quotedString = string.Empty;
    string replacedString = str.Replace(str.Substring(0, startPosition),str.Substring(0, startPosition).Insert(startPosition, "'")).Substring(0, lastPosition).Insert(lastPosition, "'");
    return String.Concat(replacedString, str.Remove(0, replacedString.Length));
}