comboBox1.DataSource = _Table;
comboBox1.DisplayMember = "!23";
comboBox1.SelectedIndex = -1;
或则comboBox1.Items.Insert(0, "请选择");
comboBox1.DisplayMember = "!23";
comboBox1.SelectedIndex = -1;
或则comboBox1.Items.Insert(0, "请选择");
combobox.Text = ""
这样就可以了.
设置SelectedIndex = -1;