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c# asp.net master page get a href and set visible to false

I have an a href link in my user.master page, but I'm unable to find that control in my user.master.cs. How do I do so? I tried using master and find control, but it says object reference is not instance to an object or it does not work. Please help, thanks.
user.master
Upgrade
user.master.cs
(first try)
var masterPage = Master;
if (masterPage != null)
{
masterPage.FindControl("showUpgradeLink").Visible = true;
}
(second try)
this.Master.FindControl("showUpgradeLink").Visible = false;

Did you put runat="server" on the a tag?
For example:
<a href="ViewPremiumPlans.aspx" id="showUpgradeLink" runat="server" class="btn-light btn-sm" >Upgrade</a>

You need to add runat="server" without that it is not a server control.
Upgrade
You then access it in the master (user.master.cs) page directly
showUpgradeLink.visible = false;
If you want to expose it to child pages add a public property to user.master.cs
public HtmlGenericControl UpgradeLink { get { return showUpgradeLink; } };
In your child aspx pages where you want to access the control/property add:
<%# MasterType virtualpath="~/Path/To/user.master" %>
Then in the child .cs pages you can use:
Page.Master.UpgradeLink.visible = false;

Is there an ASP.NET databindable control (like Repeater), which only expects a single item?

I'm trying display lots of properties from a business object on a Web Form. I could of course, create loads of labels and assign all the values in code-behind, but I feel there must be a less verbose way.
What I want is something like an asp:Panel but where you can specify a datasource. It doesn't seem like Panels support any kind of databinding.
What I'd like is something like this
// C#
panel.DataSource = theCompany;
panel.DataBind();
Then:
// ASPX
<asp:Panel runat="server">
Name: <%# Eval("Name") %>
Phone: <%# Eval("Phone") %>
...
</asp:Panel>
..but I can't find anything which will allow me to work in this way.
I thought I might be able to use asp:FormView but this just gives the error "Data source is an invalid type. It must be either an IListSource, IEnumerable, or IDataSource."
A caveat is that I do not want to call a global DataBind() (this has caused us no-end of problems in the past) - I would like the databind to be constrained to a particular part of the page.

It seems you can do this using a Panel, but you have to assign your business object to a page property first, as there's no way to set the business object as a "DataSource" for the panel (as you would for a Repeater control, for instance).
Once the object is assigned as a page property, you can then use the following syntax in the .aspx to access the properties of that object, without needing to manually assign each item to control values in code behind:
<%# Company.Name %>

You don't need to databind (although you can). What you need is a simple expression evaluator. Add a property to your code behind like this
public string Test { get; set; }
protected void Page_Load(object sender, EventArgs e)
{
Test = "<script>alert('test');</script>";
}
Then use it to render code directly to the page like this
The value: <%: Test %>
Note that the <%: syntax escapes the input. If you wish to NOT escape the input then you can use <%= syntax. Note that you don't need to have a string object you can access any properties you like for example
The value lenght: <%: Test.Length %>

Use The below:
<asp:DetailsView runat="server">
Name: <%# Eval("Name") %>
Phone: <%# Eval("Phone") %>
</asp:DetailsView>

Use DetailsView. You can add it from the Toolbox. It's for Single Row Data Presentation.
<asp:DetailsView runat="server">
Name: <%# Eval("Name") %>
Phone: <%# Eval("Phone") %>
</asp:DetailsView>

Why not using DetailsView. Its perfect for what you want. Showing single row of data only and that too in two column form.

I suggest using a standard Repeater, databound with an array containing a single item.
Repeater.DataSource = new [] { theCompany };
Repeater.DataBind();
Advantage over databinding to a Panel: you can still use the ItemType attribute, and have access to the nice strongly typed Item object and don't have to go about using Eval, i.e.:
<asp:Repeater runat="server" Id="Repeater" ItemType="CompanyViewModel">
<ItemTemplate>
Name: <%# Item.Name %>
Phone: <%# Item.Phone %>
</ItemTemplate>
</asp:Repeater>
(Replace "CompanyViewModel" with the Type of your: "theCompany".)
You can also try experimenting with DetailsView, but it's not as malleable as a Repeater.

Create your own user control that shows the properties of the objects. You can use reflection to read property names and values and display in control.
Create a property for your object in your user control. Inside user control code behind write function Show() with below code.
//Build html strin from all propeties
PropertyInfo[] properties = yourObject.GetType().GetProperties();
string lbl = "<label>{0}</label>";
string value= "<span>{0}</span>";
string tab ="\t";
StringBuilder sb = new StringBuilder();
foreach (PropertyInfo pi in properties)
{
var label = string.Format(lbl,pi.Name);
var val = string.Format(value, pi.GetValue(yourObject, null))
sb.Append(label+tab+val);
sb.Append("<br/>")
}
Response.Write(sb.ToString());
Now in your pager add that control and sets its object property in code behind like
myControl.MyObject = yourObject;
myControl.Show();

NickG's answer will work... however consider two scenarios.
If your business object is ever null, the page will crash with an "Object Reference" error. This can be avoided with a cumbersome looking
<% if(MyObject != null) { %><%= MyObject.Prop %><% } %>
... but doing that every time makes for messy code.
If your page uses PostBack processing via UpdatePanel, the business object will have to be reloaded to the property every time the Page lifecycle runs... even if that portion of the page isn't being redrawn. This is because IIS will resolve all the <%= MyObject.Prop %> references regardless, causing wasted CPU cycles and probably wasted database calls if your object is coming from a database.
For these reasons I always use a Repeater control, which is lightweight, supports ViewState, can easily be assigned a one item list, and avoids the aforementioned issues. Here's an example using the HttpContext.Current.Request object as a "business object".
<asp:Repeater ID="rptTest" runat="server">
<ItemTemplate>
Request.URL = <%# Eval("Url") %>
</ItemTemplate>
</asp:Repeater>
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
var objTest = Request; //Using the Request object as a test business object
rptTest.DataSource = new List<System.Web.HttpRequest>() { objTest };
rptTest.DataBind();
}
}

To make this work we can customize ASP.NET Panel by inheriting it and using Custom Server control for ASP.NET
Use Below Code to modify the ASP.NET Panel in an ASP.NET Custom Server Control Project:
[DefaultProperty("Text")]
[ToolboxData("<{0}:CustomPanel runat=server></{0}:CustomPanel>")]
public class CustomPanel : Panel
{
[Bindable(true)]
public object MyDataSource
{
get;
set;
}
[Bindable(true)]
[Category("Appearance")]
[DefaultValue("")]
[Localizable(true)]
public StringBuilder Text
{
get;
set;
}
public void MyDataBind()
{
Text = new StringBuilder();
foreach (PropertyInfo p in MyDataSource.GetType().GetProperties())
{
Text.Append(string.Format("<b>{0}</b>", p.Name));
Text.Append(":");
if (p.GetIndexParameters() == null || p.GetIndexParameters().Length == 0)
Text.Append(p.GetValue(MyDataSource, null));
Text.Append("<br />");
}
}
protected override void RenderContents(HtmlTextWriter output)
{
output.Write(Text);
}
}
Then add this control's reference and toolbox item to your ASP.NET page:
<cc2:CustomPanel ID="MyCustomPanel" runat="server">
</cc2:CustomPanel>
Use the control as shown below:
MyCustomPanel.MyDataSource = theCompany;
MyCustomPanel.MyDataBind();

Finding a field on user control form

I have a field 'x' on the user control form which is included on aspx page and that page using SharePoint master page. I'm trying to locate field x on aspx page in my code but it throws "Object ref not set" error. I've tried following but nothing works ,
((TextBox)Page.Master.FindControl("PlaceHolderMain").FindControl("Experience").FindControl("x")).Text
((TextBox)this.FindControl("x")).Text
((TextBox)Page.Master.FindControl("PlaceHolderMain").FindControl("x")).Text
I can locate the field on page source,
<input name="ctl00$PlaceHolderMain$ctl00$x" type="text" value="3" id="ctl00_PlaceHolderMain_ctl00_x" class="textbox" />
Update:-
Previously I was adding user control programmatically on load event of the aspx page,
UserControl uc = (UserControl)Page.LoadControl("Experience.ascx");
experineceForm.Controls.Add(uc);
But by seeing page source I had doubt and thought to add it in design time using following code,
<%# Register TagPrefix="uc" TagName="Experience" Src="Experience.ascx" %>
<div id="experineceForm" runat="server">
<uc:experience id="idExperienceForm" runat="server"/>
</div>
After doing this I'm able to find controls with following code,
((TextBox)Page.Master.FindControl("PlaceHolderMain").FindControl("idExperienceForm").FindControl("txtEmployeeComments")).Text

Try this function (below) to do a recursive search for the ID. Most probably the System.NullReferenceException: Object reference not set to an instance of an object error is because the script did not find the text box so the control did not have a .Textproperty. NB: root would be the id of an asp.net placeholder object or an asp.net panel, etc. that contains the text box you are looking for. You should test for null returns before attempting to use the control.
public Control FindControlRecursive(Control root, string id)
{
if (root.ID == id) {
return root;
}
Control c = default(Control);
foreach ( c in root.Controls) {
Control t = FindControlRecursive(c, id);
if ((t != null)) {
return t;
}
}
return null;
}

AFAIK, ((TextBox)Page.Master.FindControl("x")).Text should work

Master Page is adding additional text in TextBox ID

I have a master page which has a content section with the id cpMainContent.
I am using this master page on every webform I am creating for college project. One of such form is frmSearchPersonnel. The purpose of frmSearchPersonnel is to ask user last name of the person they want to search in a textbox and then click on search button. The ID of TextBox is
txtSearchName
Search button will do postbackUrl transfer to another form which I have named frmViewPersonnel.
In frmViewPersonnel I am trying to use following code.
NameValueCollection myRequest = Request.Form;
if(!string.IsEmptyOrNull(myRequest["txtSearchName"]))
string strSearch = myRequest["txtSearchName"];
The problem I ran into is that this didn't find any control with the name of txtSearchName. While debugging I found this in myRequest object,
[5] "ctl00$cpMainContent$txtSearchName" string
Even though when I added textbox I gave it ID of txtSearchName but when page is rendered it is adding extra string from master page.
How can I stop this? I have to use master page so don't say not to use master page :)
Why is it doing that?
Update
While Googling and Binging I found that I can use Control.ClientID in this case so looking into it.
Update 2
As suggested below to add ClientIDMode="static" in the html of control or add it in page directive. What it does is, it keeps the ID static to txtSearchName but problem is this,
<input name="ctl00$cpMainContent$txtSearchName" type="text" id="txtSearchName" />
Here name is still using ctl00 and the code I showed above,
string strSearch = myRequest["txtSearchName"]
it still won't work because nvc collection is either searchable by index or name not the id directly.
==============

You need to add a ClientIDMode="Static" to the html of the textbox:
<asp:TextBox ID="txtSearchName" runat="server" ClientIDMode="Static" />
It happens to prevent duplicate ID's. Usually it happens when you use master pages as it contains nested pages
If you want all controls with ClientIDMode="Static", you can put it in the page header of the master file.
<%# Page Language="C#" ClientIDMode="Static" %>

If you are posting to another page that uses the same master page (called SiteMaster in my case), the name of the textbox should be same the same.
string val = Request[((SiteMaster)Master).txtSearchName.UniqueID];
If you're NOT posting to a page with the same master, well, then are you using the viewstate for the textbox at all since you're posting to another page? If not, just make the control a non asp.net control:
<input type="text" name="txtSearchName"/>
If you are using viewstate and posting to another page with a different master page, well, you should use PreviousPage.

Little late here. Appreciate #aquinas and #rudeovski ze bear. Interesting and good answers.
I'd same issue and I solved it differently.
In fact, I used a public Interface.
public interface ISearch
{
string SearchText { get; }
}
Then implement ISearch interface in two aspx page say One.aspx and Two.aspx classes.
--One.aspx-- (Where I'v added TextBox1, and Button1 and set Button1.PostBackUrl="~/Two.aspx")
public partial class One : System.Web.UI.Page , ISearch
{
public string SearchText
{
get
{
return TextBox1.Text;
}
}
}
--Two.aspx--
public partial class Two : System.Web.UI.Page, ISearch
{
protected void Page_Load(object sender, EventArgs e)
{
ISearch search = (ISearch) PreviousPage;
Label1.Text = search.SearchText;
}
public string SearchText
{
get
{
throw new NotImplementedException();
}
}
}

If your try to access the input element value in code behind on post back instead of for example:
var emailAddress = Request.Form["ctl00$ctl00$ctl00$ContentContainer$MainContent$MainContent$ContentBottom$ProfileFormView$emailaddress1"];
Use
var emailAddressKeyName = Request.Form.AllKeys.FirstOrDefault(a => a.Contains("emailaddress1"));
var emailAddress = Request.Form[emailAddressKeyName];

Acess controls on ContentPages via Javascript by MasterPage

I need my MasterPage to be able to get ControlIDs of Controls on ContentPages, but I cannot
use <%= xxx.CLIENTID%> as it would return an error as the control(s) might not be loaded by the contentplaceholder.
Some controls have a so called BehaviourID, which is exactly what I would need as they can be directly accessed with the ID:
[Asp.net does always create unique IDs, thus modifies the ID I entered]
Unfortunately I need to access
e.g. ASP.NET Control with BehaviouraID="test"
....
document.getElementById("test")
if I were to use e.g. Label control with ID="asd"
....
document.getElementById('<%= asd.ClientID%>')
But if the Labelcontrol isn't present on the contentpage, I of course get an error on my masterpage.
I need a solution based on javascript. (server-side)
Thx :-)

You could use jQuery and access the controls via another attribute other than the ID of the control. e.g.
<asp:Label id="Label1" runat="server" bid="test" />
$('span[bid=test]')
The jQuery selector, will select the span tag with bid="test". (Label renders as span).

Best solution so far:
var HiddenButtonID = '<%= MainContent.FindControl("btnLoadGridview")!=null?
MainContent.FindControl("btnLoadGridview").ClientID:"" %>';
if (HiddenButtonID != "") {
var HiddenButton = document.getElementById(HiddenButtonID);
HiddenButton.click();
}
Where MainContent is the contentplace holder.
By http://forums.asp.net/members/sansan.aspx

You could write an json-object with all the control-ids which are present on the content-page and "register" that object in the global-scope of your page.
Some pseudo pseudo-code, because I can't test it at the moment...
void Page_Load(object sender,EventArgs e) {
System.Text.StringBuilder clientIDs = new System.Text.StringBuilder();
IEnumerator myEnumerator = Controls.GetEnumerator();
while(myEnumerator.MoveNext()) {
Control myControl = (Control) myEnumerator.Current;
clientIDs.AppendFormat("\t\"{0}\" : \"{1}\",\n", myControl.ID, myControl.ClientID);
}
page.ClientScript.RegisterStartupScript(page.GetType(),
"ClientId",
"window.ClientIDs = {" + clientIDs.ToString().Substring(0, clientIDs.ToString().Length - 2) + "};",
true);
}

It sounds like your issue is that you are using the master page for something it wasn't intended. The master page is a control just like any other control, and therefore cannot access any of the controls of its parent (the page). More info:
ASP.Net 2.0 - Master Pages: Tips, Tricks, and Traps
My suggestion is to inject the JavaScript from your page where the controls can actually be resolved. Here is a sample of how this can be done:
#Region " LoadJavaScript "
Private Sub LoadJavaScript()
Dim sb As New StringBuilder
'Build the JavaScript here...
sb.AppendFormat(" ctl = getObjectById('{0});", Me.asd.ClientID)
sb.AppendLine(" ctl.className = 'MyClass';")
'This line adds the javascript to the page including the script tags.
Page.ClientScript.RegisterClientScriptBlock(Me.GetType, "MyName", sb.ToString, True)
'Alternatively, you can add the code directly to the header, but
'you will need to add your own script tags to the StringBuilder before
'running this line. This works even if the header is in a Master Page.
'Page.Header.Controls.Add(New LiteralControl(sb.ToString))
End Sub
#End Region