如何在MVC3中使用c#代码使标签可见？

Question

Following is the Label in my view page,

 <label id="back"  onclick="BacktoSubmit()"  style="cursor:pointer; text-decoration:underline; color:Blue; padding-left:670px; visibility:hidden;">Back to list</label>

Following is my Controller Method,

   public ActionResult TRSkillGradeAvailability(FormCollection frmCollection, string Submit, string Search, string TabType)
    {
        try
        {
            string strLoggedUser = GetLogUser();
            TRSkillGradeAvailabilityModel objTRSkillGradeAvailabilityModel = new TRSkillGradeAvailabilityModel();
            TRSkillGradeAvailabilityModel objTRSkillGradModel = new TRSkillGradeAvailabilityModel();
            TravelReadyCommonModel objTravelReadyCommonModel = new TravelReadyCommonModel();
            string strVertical = string.Empty, strGeo = string.Empty, strGrade = string.Empty, strSkill = string.Empty;
            strVertical = Convert.ToString(frmCollection["ddlVertical"]);
            strGeo = Convert.ToString(frmCollection["ddlGeo"]);
            strGrade = Convert.ToString(frmCollection["ddlGrade"]);
            strSkill = Convert.ToString(frmCollection["ddlSkill"]);
            AssignViewBag(strVertical, strGeo, strGrade, strSkill);


            var button = Submit ?? Search;
            if (button != "Submit")
            {

                if (button == null)
                {
                    button = "Search";
                }
            }
            if (TabType == "1")
            {
                TempData["Tab"] = "1";
                if (button == "Search")
                {                       
                    Label lbl = new Label();
                    lbl.FindControl("back").Visible = true;
                    string strSearchId = string.Empty;
                    strSearchId = Convert.ToString(frmCollection["txtSearch"]).Trim();
                    objTRSkillGradeAvailabilityModel = objTRSkillGradeAvailabilityModel.GetTRPoolData(strVertical, strGeo, strSkill, strGrade, 3, strSearchId, strLoggedUser);
                }
                else if (button == "Submit")
                {
                    if (strVertical == TravelReadyContants.StaticVariable.AllVertical)
                        objTRSkillGradeAvailabilityModel = objTRSkillGradeAvailabilityModel.GetTRPoolData(strVertical, strGeo, strSkill, strGrade, 1, string.Empty, strLoggedUser);
                    else
                        objTRSkillGradeAvailabilityModel = objTRSkillGradeAvailabilityModel.GetTRPoolData(strVertical, strGeo, strSkill, strGrade, 2, string.Empty, strLoggedUser);
                }
            }
            else if (TabType == "2")
            {
                TempData["Tab"] = "2";
                objTRSkillGradeAvailabilityModel = objTRSkillGradeAvailabilityModel.GetMyPoolData(strLoggedUser);
                if (button == "Search")
                {
                    string strSearchId = string.Empty;
                    strSearchId = Convert.ToString(frmCollection["txtSearch"]).Trim();
                    objTRSkillGradeAvailabilityModel.lstTRSkillGradeAvailabilty = objTRSkillGradeAvailabilityModel.lstTRSkillGradeAvailabilty.FindAll(List => List.AssocId == strSearchId);
                }
                else if (button == "Submit")
                {
                    if (strVertical != TravelReadyContants.StaticVariable.AllVertical)
                        objTRSkillGradeAvailabilityModel.lstTRSkillGradeAvailabilty = objTRSkillGradeAvailabilityModel.lstTRSkillGradeAvailabilty.FindAll(List => List.Geo == strGeo && List.Vertical == strVertical && List.SkillName == strSkill && List.GradeName == strGrade);
                    else
                        objTRSkillGradeAvailabilityModel.lstTRSkillGradeAvailabilty = objTRSkillGradeAvailabilityModel.lstTRSkillGradeAvailabilty.FindAll(List => List.Geo == strGeo && List.SkillName == strSkill && List.GradeName == strGrade);
                }
            }

            GetdropdownValues(ref objTravelReadyCommonModel, ref objTRSkillGradModel, 1, string.Empty);
            objTRSkillGradeAvailabilityModel.LoggedInUser = strLoggedUser;
            objTRSkillGradeAvailabilityModel.lstGeo = objTravelReadyCommonModel.lstGeo;
            objTRSkillGradeAvailabilityModel.lstGrade = objTRSkillGradModel.lstGrade;
            objTRSkillGradeAvailabilityModel.lstSkill = objTRSkillGradModel.lstSkill;
            objTRSkillGradeAvailabilityModel.DefaultGeo = objTRSkillGradModel.DefaultGeo;
            objTRSkillGradeAvailabilityModel.DefaultGrade = objTRSkillGradModel.DefaultGrade;
            objTRSkillGradeAvailabilityModel.DefaultSkill = objTRSkillGradModel.DefaultSkill;

            GetdropdownValues(ref objTravelReadyCommonModel, ref objTRSkillGradModel, 2, strGeo);
            objTRSkillGradeAvailabilityModel.lstVerticals = objTravelReadyCommonModel.lstVerticals;
            objTRSkillGradeAvailabilityModel.DefaultVertical = objTRSkillGradModel.DefaultVertical;

            return View(objTRSkillGradeAvailabilityModel);
        }
        catch (Exception ex)
        {
            ILogManager LogManager = new LogManager();
            var frame = new StackFrame(0);
            LogManager.CallLogging(frame, ex.Message, ex.StackTrace);
            return RedirectToAction("Error", "Common");
        }
    }

in this method i've used,

     Label lbl = new Label();
     lbl.FindControl("back").Visible = true;

this code to make the label visible while click the search button but it shows 'NullReferenceException' How to fix this issue anyother way to make the label visible when click search button?

Answer 1

You can add one more property to your model of type string like visible

public string Visibility { get; set; }

Set this model property

if (button == "Search")
{
         objTRSkillGradeAvailabilityModel.Visibility = "visible";         
}

else
      objTRSkillGradeAvailabilityModel.Visibility = "hidden";         

and in view

<label id="back" name="back" style="visibility:@Model.Visibility"/>

Answer 2

@Html.Label("", "无效的账户 ID 或付款未支付。", htmlAttributes: new { @class = "control-label col", style = "color:#ff0000", hidden="false" })