how to join the data from the string

i am using this code..
string[] SplitTextBox = txt_cities.Text.Split('-');
in this i retrieve the value
 
string[0] = "Bangkok"string[1] = "Bangkok"string[2] = "Bangkok"string[3] = "Bangkok"string[4] = "Lopburi"string[5] = "Sri Satchanalai Historic park"string[6] = "Phitsanulok"string[7] = "Sukhothai"string[8] = "Phitsanulok"string[9] = "Bangkok"
 
now i want to join these values distinctly
 
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