How can I put quotes in a string?

You need to escape the quotation marks to put them in a string. There is two ways of doing this. Using backslashes in a regular string:

writeText.WriteLine("<?xml version=\"1.0\" encoding=\"utf-8\"?>");

Using double quoation marks in a @-delimited string:

writeText.WriteLine(@"<?xml version=""1.0"" encoding=""utf-8""?>");

Try

writeText.WriteLine("<?xml version=\"1.0\" encoding=\"utf-8\"?>");

Have a look at "What character escape sequences are available?" of the C# FAQ

Since to XML both " and ' can used, try

writeText.WriteLine("<?xml version='1.0' encoding='utf-8'?>");

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