我在asp.net页面中有一个标签，并在某些情况下更改其文本。这是代码：
<asp:Label ID="errorMessage" runat="server" Text="Label" Visible="False"></asp:Label>
errorMessage.Text = MyGlobals.student.registerCourse(c, ref addList, course).ToString();
errorMessage.ForeColor = System.Drawing.Color.Red;
errorMessage.Visible = true;
当我调试时，我看到MyGlobals.student.registerCourse（c，ref addList，course）.ToString（）方法很好地返回了我的错误信息。然后我将标签设置为可见，但是当页面加载时我看不到标签。此外，在调试时，我看到标签的“textsetbyaddparsedsubobject”属性为false。这可能是问题吗？为什么我的页面中没有显示标签？有人可以帮忙吗？
感谢。
编辑：以下是完整代码：
protected void bSubmitChanges_Click1(object sender, EventArgs e)
{
Userfunctions function = new Userfunctions();
List<string> dropList = new List<string>();
List<string> addList = new List<string>();
SqlConnection con = new SqlConnection();
con.ConnectionString = Userfunctions.GetConnectionString();
SqlCommand cmd;
con.Open();
string ID = MyGlobals.currentID;
try
{
for (int i = 1; i <= 6; i++)
{
string course;
if ((course = boxCRN(i)) != "")
{
cmd = new SqlCommand("select count (*) from CourseTable where CRN=@course", con);
cmd.Parameters.AddWithValue("@course", course);
int result = Convert.ToInt32(cmd.ExecuteScalar());
if (result > 0)
{
cmd = new SqlCommand("select * from CourseTable where CRN=@course", con);
cmd.Parameters.AddWithValue("@course", course);
cmd.ExecuteScalar();
SqlDataAdapter da = new SqlDataAdapter(cmd);
DataTable dt = new DataTable();
da.Fill(dt);
foreach (DataRow dr in dt.Rows)
{
string query = "SELECT * FROM CourseTable WHERE CourseCode='" + dr["CourseCode"] + "' AND CourseNumber='" + dr["CourseNumber"] + "' AND Term='" + dr["Term"] + "'";
cmd = new SqlCommand(query, con);
SqlDataAdapter da2 = new SqlDataAdapter(cmd);
DataTable dt2 = new DataTable();
da2.Fill(dt2);
DataRow dr2 = dt2.Rows[0];
cmd = new SqlCommand("select * from PrereqTable where CourseCode='" + dr["CourseCode"] + "' AND CourseNumber='" + dr["CourseNumber"] + "' AND Term='" + dr["Term"] + "'", con);
da2 = new SqlDataAdapter(cmd);
dt2 = new DataTable();
da2.Fill(dt2);
List<string> pre = new List<string>();
foreach (DataRow dr5 in dt2.Rows)
{
pre.Add(Convert.ToString(dr5["pCourseCode"]) + Convert.ToString(dr5["pCourseNumber"]));
}
Course c = new Course(dr2["InstructorID"].ToString(), dr2["CourseCode"].ToString(), dr2["CourseNumber"].ToString(), dr2["CourseName"].ToString(), dr2["Term"].ToString(), dr2["CRN"].ToString(), dr2["Level"].ToString(), dr2["Credit"].ToString(), dr2["Description"].ToString(), dr2["Capacity"].ToString());
c.addPrereq(pre);
string message = MyGlobals.student.registerCourse(c, ref addList, course).ToString();
errorMessage.Text = message;
errorMessage.ForeColor = System.Drawing.Color.Red;
errorMessage.Visible = true;
Label1.Visible = true;
Label1.Text = "asdasdasd";
}
}
}
}
}
catch (Exception) { }
for (int i = 0; i < showCourses.Rows.Count; i++)
{
string a = ((DropDownList)showCourses.Rows[i].FindControl("actionmenu")).SelectedValue;
if (((DropDownList)showCourses.Rows[i].FindControl("actionmenu")).SelectedValue == "1")
{
string courseCode = showCourses.Rows[i].Cells[1].Text, courseNumber = showCourses.Rows[i].Cells[2].Text;
SqlCommand com = new SqlCommand("select * from CourseTable where CourseCode=@courseCode and CourseNumber=@courseNumber", con);
com.Parameters.AddWithValue("courseCode", courseCode);
com.Parameters.AddWithValue("courseNumber", courseNumber);
try
{
SqlDataAdapter da2 = new SqlDataAdapter(com);
DataTable dt2 = new DataTable();
da2.Fill(dt2);
DataRow dr2 = dt2.Rows[0];
Course c = new Course(dr2["InstructorID"].ToString(), dr2["CourseCode"].ToString(), dr2["CourseNumber"].ToString(), dr2["CourseName"].ToString(), dr2["Term"].ToString(), dr2["CRN"].ToString(), dr2["Level"].ToString(), dr2["Credit"].ToString(), dr2["Description"].ToString(), dr2["Capacity"].ToString());
Register reg = new Register(c, MyGlobals.student);
MyGlobals.student.dropCourse(reg);
dropList.Add(showCourses.Rows[i].Cells[1].Text + showCourses.Rows[i].Cells[2].Text);
}
catch (Exception) { }
}
}
foreach (string course in dropList)
{
for (int i = 0; i < MyGlobals.student.getRegistered().Count; i++ )
{
if (MyGlobals.student.getRegistered()[i].getCourse().getCode().ToString() + MyGlobals.student.getRegistered()[i].getCourse().getNumber().ToString() == course)
MyGlobals.student.dropCourse(MyGlobals.student.getRegistered()[i]);
}
cmd = new SqlCommand("delete from RegisterTable where StudentID='" + MyGlobals.currentID + "' and CourseCode='" + course.Substring(0, course.Length - 3) + "' and CourseNumber='" + course.Substring(course.Length - 3, 3) + "'", con);
cmd.ExecuteNonQuery();
}
try
{
foreach (string courses in addList)
{
string courseCode = "";
string courseNumber = "";
string term = MyGlobals.currentTerm + " " + MyGlobals.currentYear;
string q = ("select CourseCode from CourseTable where CRN=@courses");
string grade = "";
SqlCommand command = new SqlCommand(q, con);
command.Parameters.AddWithValue("@courses", courses);
courseCode = Convert.ToString(command.ExecuteScalar());
q = ("select CourseNumber from CourseTable where CRN=@courses");
command = new SqlCommand(q, con);
command.Parameters.AddWithValue("@courses", courses);
courseNumber = Convert.ToString(command.ExecuteScalar());
cmd = new SqlCommand("insert into RegisterTable (CourseCode,CourseNumber,Term,StudentID,Grade) values(@courseCode,@courseNumber,@term, @ID,'U')", con);
cmd.Parameters.AddWithValue("@courseCode", courseCode);
cmd.Parameters.AddWithValue("@courseNumber", courseNumber);
cmd.Parameters.AddWithValue("@term", term);
cmd.Parameters.AddWithValue("@ID", ID);
cmd.Parameters.AddWithValue("@grade", grade);
cmd.ExecuteNonQuery();
}
}
catch (Exception) { }
con.Close();
Response.Redirect("AddDropClasses.aspx");
}
}
注册课程功能：
public string registerCourse(Course course, ref List <string> addList, string crn) {
bool registered = true;
string message ="";
foreach (string s in course.getTime())
{
Userfunctions f = new Userfunctions();
foreach (Register r in this.register) {
if (r.getCourse().getTerm() == MyGlobals.currentTerm.ToString() + " " + MyGlobals.currentYear.ToString() && !f.TimeCheck(s, r.getCourse().getTime()))
{
registered = false;
message = "Time conflict";
}
}
}
if (registered) {
SqlConnection con = new SqlConnection();
con.ConnectionString = Userfunctions.GetConnectionString();
con.Open();
string id = MyGlobals.currentID;
SqlCommand cmd = new SqlCommand("SELECT count (*) from RegisterTable where CourseCode ='" + course.getCode() +"' and CourseNumber='" + course.getNumber() + "' and Term='" + course.getTerm()+"'" , con);
cmd.Parameters.AddWithValue("@id", id);
int active = Convert.ToInt32(cmd.ExecuteScalar());
if (active >= Convert.ToInt32(course.getCapacity())){
registered = false;
message = "Not enough capacity";
}
if (registered) {
foreach (string s in course.getPrerequisites()) {
if (!hasPassedCourse(s)) {
registered = false;
message = "Prerequisite error";
}
}
}
}
if (registered)
{
Register reg = new Register(course, MyGlobals.student);
MyGlobals.student.addToSchedule(reg);
addList.Add(crn);
}
return message;
}
答案 0 :(得分：2)
删除以下行
Response.Redirect("AddDropClasses.aspx");
它会再次将您的页面加载为新页面
答案 1 :(得分：-1)
如果在控件上设置 Visible =“false”，则控件属性可能未完全实例化。
我会尝试在Page_Load的代码隐藏中使用 errorMessage.Visible = false 隐藏控件。