AutoCompleteStringCollection UnameCustomSource = new AutoCompleteStringCollection();
            UnameCustomSource.AddRange(string[]);
            textBox1.AutoCompleteSource = AutoCompleteSource.CustomSource;
            textBox1.AutoCompleteMode = AutoCompleteMode.Suggest;
            textBox1.AutoCompleteCustomSource = UnameCustomSource;

------解决方案--------------------

lz用VB的...那是VS的内部功能，你得像微软提建议...但是...估计微软不会理你...