I am trying to get previous page title in my asp.net application.
My attempt :
string previousPageTitle = this.Page.PreviousPage.Title;
I am getting "NullReferenceException" as Object reference not set to an instance of an object.
I do not want to use session or query string to get previous page title.
See this SO question.
Is the reference to this.Page returning null? You could try accessing it through the HttpContext object:
((Page)HttpContext.Current.Handler).PreviousPage.Title
I believe you are going to the page directly, thus resulting in PreviousPage being null.
See Page.PreviousPage property
When you use the Transfer method or use cross-page posting to transfer
processing from one ASP.NET page to another, the originating page
contains request information that might be required for the
destination page. You can use the PreviousPage property to access that
information. If the current page is being rendered as a result of a
direct request (not a transfer or cross-post from another page), the
PreviousPage property contains null.
Related
I'm trying to get the path for all the .aspx-files that has a specific MasterPageFile value.
Lets say I have a aspx-file called "hi.aspx" with the MasterPageFile="hello.Master" in the page directive. I want to get the value from the MasterPageFile property through reflection, in a method like so:
GetAllASpxFilesUsingMasterFile("~/hello.Master");
> hi.aspx
The problem Im having using:
var type = BuildManager.GetCompiledType(path)
Activator.CreateInstance(type)
is that the MasterPageFile-property is null.. ideas?
You have just called the constructor and created a new instance that´s why MasterPageFileProperty is null. There is no page life cycle involved which is necessary for populating pages with controls and properties.
To get the actual page life cycle process going you should call ProcessRequest() method but this is not advised at all.
Type type = BuildManager.GetCompiledType("~/Default.aspx");
Page myPage = (Page)Activator.CreateInstance(type);
myPage.ProcessRequest(HttpContext.Current);
I have login page, once logged in I create a session variable to store the UserName.
I've used this variable to retrieve info for this User from Account table with AccountID, name etc and I return the AccountID on the page using a label (lblAccountID).
I have a button to "Add Funds" to this account, which redirects to the AddFunds.aspx page
How can I pass the AccountID into the AddFunds.aspx page which will be used to insert details into Funds table which has the AccountID.
I don't want the AccountID to be visible on the AddFunds.aspx page.
there are multiple ways to achieve this. i can explain you in brief about the 4 types which we use in our daily programming life cycle.
Please go through the below points.
1 Query String.
FirstForm.aspx.cs
Response.Redirect(“SecondForm.aspx?Parameter=” + TextBox1.Text);
SecondForm.aspx.cs
TextBox1.Text = Request. QueryString["Parameter"].ToString();
This is the most reliable way when you are passing integer kind of value or other short parameters.More advance in this method if you are using any special characters in the value while passing it through query string, you must encode the value before passing it to next page. So our code snippet of will be something like this:
FirstForm.aspx.cs
Response.Redirect(“SecondForm.aspx?Parameter=” + Server.UrlEncode(TextBox1.Text));
SecondForm.aspx.cs
TextBox1.Text = Server.UrlDecode(Request.QueryString["Parameter"].ToString());
2. Passing value through context object
Passing value through context object is another widely used method.
FirstForm.aspx.cs
TextBox1.Text = this.Context.Items["Parameter"].ToString();
SecondForm.aspx.cs
this.Context.Items["Parameter"] = TextBox1.Text;
Server.Transfer(“SecondForm.aspx”, true);
Note that we are navigating to another page using Server.Transfer instead of Response.Redirect.Some of us also use Session object to pass values. In that method, value is store in Session object and then later pulled out from Session object in Second page.
3. Posting form to another page instead of PostBack
Third method of passing value by posting page to another form. Here is the example of that:
FirstForm.aspx.cs
private void Page_Load(object sender, System.EventArgs e)
{
buttonSubmit.Attributes.Add(“onclick”, “return PostPage();”);
}
And we create a javascript function to post the form.
SecondForm.aspx.cs
function PostPage()
{
document.Form1.action = “SecondForm.aspx”;
document.Form1.method = “POST”;
document.Form1.submit();
}
TextBox1.Text = Request.Form["TextBox1"].ToString();
Here we are posting the form to another page instead of itself. You might get viewstate invalid or error in second page using this method. To handle this error is to put EnableViewStateMac=false
4. Another method is by adding PostBackURL property of control for cross page post back
In ASP.NET 2.0, Microsoft has solved this problem by adding PostBackURL property of control for cross page post back. Implementation is a matter of setting one property of control and you are done.
FirstForm.aspx.cs
<asp:Button id=buttonPassValue style=”Z-INDEX: 102″ runat=”server” Text=”Button” PostBackUrl=”~/SecondForm.aspx”></asp:Button>
SecondForm.aspx.cs
TextBox1.Text = Request.Form["TextBox1"].ToString();
In above example, we are assigning PostBackUrl property of the button we can determine the page to which it will post instead of itself. In next page, we can access all controls of the previous page using Request object.
You can also use PreviousPage class to access controls of previous page instead of using classic Request object.
SecondForm.aspx
TextBox textBoxTemp = (TextBox) PreviousPage.FindControl(“TextBox1″);
TextBox1.Text = textBoxTemp.Text;
As you have noticed, this is also a simple and clean implementation of passing value between pages.
Reference: "How to: Pass Values Between ASP.NET Web Pages"
You need to store it in a session variable:
int AccountIdVar;
Session["AccountID"] = AccountIdVar;
then you can retrieve later by
int AccountIdVar = (int)Session["AccountID"];
You can either use the session variable you stored in the previous page as it should still be accessible or another way is to pass the id over via a querystring such as www.foofoofoo.com?Id=23456.
As the others said, you can use Session or Querystring values. You can also just POST to the new page
The How To Pass Values Between Pages page is worth looking at too.
The MSDN article about Pass Values Between ASP.NET Web Pages is the best place to look for.
For this we can also use Global variable, create a module class in that declare all variables with public data type, then assign the values. Once the value is assigned it can be accessed from anywhere.
how can i send object from page to page in asp.net?
Have you thought about using a Session variable? You can save your object to a session varible and then retrieve it from the called page.
Here's an example:
Set from one page
Session["myobject"] = MyObject;
Retrieve from another
MyObject o = Session["myobject"]
You can use the Session to store a user-specific object between pages, or send data via a form GET or POST. There is also PreviousPage for a cross-page postback.
Session
Database
Context Cache
XML/Text File
Post/Get
Azure
Querystring
Pure willpower ;)
The problem is I redirect to a sub page from the main page by passing a few values in Request.
I need to get back the value I got from manipulating values I sent in request and I don't need to store value in Session.
You can use the PreviousPage property, depending on how you got to the new page.
There are a number of things you can do:
Page.Request["ID_Of_Control_You_Are_Interested_In"] will get you a value that you need.
If you Server.Transfer to the page you can call Context.Handler, cast it to the page you come from and traverse the controls collection to get your value.... (similar to PreviousPage property)
You can also inspect the Query string parameters sent in the request too:
Page.Request.QueryString("Param_To_Inspect")
you can return your values as JSON as the response and then using a jquery to get the data
You have three options: Query String Parameters, Cookies and Session State
Query String Parameters: http://www.aspnet101.com/2007/11/using-the-querystringparameter/
This is a good way to pass data between pages. It's the most commonly used and is limited to the max length of the url.
Cookies : http://msdn.microsoft.com/en-us/library/ms178194.aspx
This is a good method. It also has a size limitation. The advantage of cookies is you can persist data that can span visits to your site.
Session State : http://msdn.microsoft.com/en-us/library/ms178581.aspx
This an ok method, I'd use the two methods above before I would use session state. In my experience you can get into trouble very fast with Session state.
To answer your question: You can take the value from the request and load it into a TextBox. Then on the web page, the user edits the value and clicks a save button, which posts the changed value back to the server.
Or you could use javascript to post the value back to the server.
i want a handler to redirect to a web-forms page, pre-filling in the values of some controls on the form.
i tried setting my current Request.Form data:
if (theyWantToDoSomething)
{
//pre-fill form values
context.Request.Form["TextBox1"] = "test";
context.Request.Form["ComboBox1"] = "test 2";
context.Request.Form["TextBox2"] = GetTheTextForTheThing();
//tell the client to go there
context.Response.Redirect("~/SomeWebForm.aspx");
return;
}
But i get an exception that Form values are read only.
What would be a way to send the client to another page, pre-filling form data?
Answer
i used the Session state to store values. It's important to note that by default a Handler doesn't have access to Session (the Session object will be null). You have to tell IIS to give you the Session object by adding the IRequiresSessionState marker interface to your handler class:
public class Handler : IHttpHandler, System.Web.SessionState.IRequiresSessionState
{
public void ProcessRequest(HttpContext context)
{
...
if (theyWantToDoSomething)
{
//pre-fill form values
context.Session["thing1"] = "test";
context.Session["thing2"] = "test 2";
context.Session["thing3"] = GetTheTextForTheThing();
//tell the client to go there
context.Response.Redirect("~/SomeWebForm.aspx");
return; //not strictly needed, since Redirect ends processing
}
...
}
}
You can only populate your Response, the Request is input data and is indeed read-only.
If you are using ASP.NET, there are a variety of ways you could accomplish what you need:
The best way would probably be to pass the data you need to be pre-populated to SomeWebForm.aspx via the Session object, and on that pages Load method, populate your form. Keep in mind that when you do Response.Redirect, a 302 response is sent to the client with the URL the client should redirect to. The process is transparent to the user...but there is a full round trip involved.
Another alternative to populating the users Session would be to add GET parameters via a query string to the redirect to SomeWebForm.aspx.
If you need to transfer processing to the SomeWebForm.aspx page without round tripping, you could use Server.Transfer. This will transfer execution from the current page to the page you choose...however, this can cause some odd behavior on the client end because the URL does not update. As far as the user is concerned, it will still appear as though they are on the same page they started on.
A few ideas that might get you started:
Pass the values in the query string
Store the values in the session state or in a seperate cookie
Store the values in HttpContext.Items and use Server.Transfer instead of Response.Redirect
Another approach that hasn't been mentioned yet is using Server.Transfer makes it possible to use the Page.PreviousPage property, allowing access to the controls on the page that transferred control.
As jrista mentioned though, using Transfer doesn't update the URL shown to the user, which may or may not be an issue. For example, a user can't precisely bookmark a page they got transferred to since the URL will be that of the original transferring page.