Regex.Matches c# double quotes
keywords = 'peace "this world" would be "and then" some'


    // Match all quoted fields
    MatchCollection col = Regex.Matches(keywords, @"'(.*?)'");

    // Copy groups to a string[] array
    string[] fields = new string[col.Count];
    for (int i = 0; i < fields.Length; i++)
    {
        fields[i] = col[i].Groups[1].Value; // (Index 1 is the first group)
    }// Match all quoted fields
    MatchCollection col = Regex.Matches(keywords, @"'(.*?)'");

    // Copy groups to a string[] array
    string[] fields = new string[col.Count];
    for (int i = 0; i < fields.Length; i++)
    {
        fields[i] = col[i].Groups[1].Value; // (Index 1 is the first group)
    }

MatchCollection col = Regex.Matches(keywords, "\"(.*?)\"");

string pattern = @"""([^""]|"""")*""";
// or (same thing):
string pattern = ""(^"|"")*"";

"(^"|"")*"

"(.*?)"

"([^"]*)"

var pattern = ""(.*?)"";

var pattern = ""([^"]*)"";

[Test]
public void Test()
{
    string input = "peace "this world" would be 'and then' some";
    MatchCollection matches = Regex.Matches(input, @"(?<=(['""])).*?(?=1)");
    Assert.AreEqual("this world", matches[0].Value);
    Assert.AreEqual("and then", matches[1].Value);
}