Asp.NET DropDownList SelectedItem.Value not changing

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Answer 1

So this answer is the "obvious" solution to the most common cause. However, there is one more surprising issue that can cause this! My list values came from a database and the values had linefeed and carriage return: "\r\n". These values look like an innocent space, but actually they are not! My solution was to remove these hidden Char values. Hope it helps.