c#学生选课系统课程设计

Box2.Text = ""; textBox3.Text = ""; textBox4.Text = "";}} private void lklbFh_LinkClicked( object sender, ** ** LinkLabelLinkClickedEventArgs e) { TeacherLogin t= new TeacherLogin (); t.ShowDialog(); this .Close(); } private void btSc_Click( object sender, EventArgs e) { if (textBox1.Text == "" && textBox2.Text == "" && textBox3.Text == "" && textBox4.Text == "") MessageBox .Show( "请选择并输入要删除的课程条件! " ); else { if (textBox1.Text != ""){ MessageBox .Show( " 确定根据课程号删除吗?删除后将无法恢复" ); string con = Program .constr; SqlConnection conn = new SqlConnection (con); string sql = "delete course o='" + textBox1.Text + "'"; mand m = new mand (sql, conn); conn.Open(); m.ExecuteNonQuery(); conn.Close(); } else if (textBox2.Text != ""){ MessageBox .Show( " 确定根据课程名删除吗?删除后将无法恢复" ); string con = Program .constr;