//查询按钮 private void button1_Click(object sender, EventArgs e) { try { if (FormMain.Power == "学生") { DBOperate operate = new DBOperate(); string name = operate.GetName(); string str1 =//创建查询字符串 "select A.stu_class as 班级,A.stu_id as 学号,A.stu_name as 姓名,B.Cour_Name as 课程名,B.Score as 成绩 from Student as A JOIN SC_result AS B ON A.stu_id=B.Stu_Id join Coures as C ON C.Cour_Id=B.Cour_Id where A.stu_name='" + name + "' and C.Cour_Semester='" + cbbSemester.SelectedItem.ToString() + "' and B.Cour_Name='" + cbbCourse.SelectedItem.ToString() + "'"; operate.BindDataGridView(dataGridView1, str1); } else { if (cbbCourse.Text == "") { string str =//创建查询字符串 "select A.stu_class as 班级,A.stu_id as 学号,A.stu_name as 姓名,B.Cour_Name as 课程名,B.Score as 成绩 from Student as A JOIN SC_result AS B ON A.stu_id=B.Stu_Id join Coures as C ON C.Cour_Id=B.Cour_Id where A.stu_name='" + cbbstudent.SelectedItem.ToString() + "' and C.Cour_Semester='" + cbbSemester.SelectedItem.ToString() + "' and A.Stu_class='" + cbbClass.SelectedItem.ToString() + "'"; operate.BindDataGridView(dataGridView1, str); } else { string str = //创建查询字符串 "select A.stu_class as 班级,A.stu_id as 学号,A.stu_name as 姓名,B.Cour_Name as 课程名,B.Score as 成绩 from Student as A JOIN SC_result AS B ON A.stu_id=B.Stu_Id join Coures as C ON C.Cour_Id=B.Cour_Id where B.Cour_Name='" + cbbCourse.SelectedItem.ToString() + "' and C.Cour_Semester='" + cbbSemester.SelectedItem.ToString() + "' and A.Stu_class='" + cbbClass.SelectedItem.ToString() + "'"; operate.BindDataGridView(dataGridView1, str); //将查询信息绑定到DATAGRIDVIEW控件 } } } catch { MessageBox.Show("你还有未选择的项", "错误", MessageBoxButtons.OK, MessageBoxIcon.Warning); } }