I am trying to create a custom control and the render method is shown below.
I get an "Object reference not set to an instance of an object" error on the bulletList.RenderControl(Writer); line.
Any ideas?
protected override void Render(HtmlTextWriter Writer)
{
if (TermSetList != null && TermSetList.Count > 0)
{
BulletedList bulletList = new BulletedList();
bulletList.Click += new BulletedListEventHandler(BulletListItem_Click);
bulletList.DisplayMode = BulletedListDisplayMode.LinkButton;
bulletList.CssClass = "tabs";
foreach (KeyValuePair<String, String> item in TermSetList)
{
ListItem listItem = new ListItem();
listItem.Text = item.Key;
listItem.Value = item.Value;
bulletList.Items.Add(listItem);
}
if (!this.Page.IsPostBack)
{
bulletList.Items[0].Selected = true;
}
bulletList.RenderControl(Writer);
base.Render(Writer);
}
}
You generally do not want to add controls during render. How your currently doing this will ensure that your click handler never gets called.
My guess as to why you are getting the error is that the control has not been added to the controls collection.
My suggestion is to move the logic to an earlier event, perhaps onload, you would not need to override the Render method then.
Related
Please refer the attached screenshot. I have an array of the checkbox and a button for the post back in ASP.Net page. I have written a function as follows to determine what all check boxes have been checked on the button click event: The following code is a part of the business component which is called from ASP.Net. Please let me know how can I return actionArray back to calling functon in ASP.Net page.
public void checkBoxValidation(Control parent, string strKey)
{
XmlDocument getCyleXML = new XmlDocument();
string strChkID="", strActionXPath = "",strAction="";
ArrayList actionArray = new ArrayList();
// Loop through all the controls on the page
foreach (Control c in parent.Controls)
{
// Check and see if it's a checkbox.
if ((c.GetType() == typeof(CheckBox)))
{
// Since its a checkbox, see if this is checked.
if (((CheckBox)(c)).Checked == true)
{
// Find the ID of the checkbox
strChkID = ((CheckBox)(c)).ID.ToString();
getCyleXML = CycleXML(strKey);
strActionXPath = "/Actions/Action[checkbox='" + strChkID + "']/*[self::Name]";
strAction = getCyleXML.SelectSingleNode(strActionXPath).ToString();
actionArray.Add(strAction);
}
}
// Now we need to call itself (recursion) because all items (Panel, GroupBox, etc) is a container so we need to check
// all containers for any checkboxes.
if (c.HasControls())
{
checkBoxValidation(c, strKey);
}
}
}
The code should be like this :
public ArrayList checkBoxValidation(Control parent, string strKey, ArrayList actionArray)
{
XmlDocument getCyleXML = new XmlDocument();
string strChkID="", strActionXPath = "",strAction="";
if(actionArray == null) { actionArray = new ArrayList(); }
// Loop through all the controls on the page
foreach (Control c in parent.Controls)
{
// Check and see if it's a checkbox.
if ((c.GetType() == typeof(CheckBox)))
{
// Since its a checkbox, see if this is checked.
if (((CheckBox)(c)).Checked == true)
{
// Find the ID of the checkbox
strChkID = ((CheckBox)(c)).ID.ToString();
getCyleXML = CycleXML(strKey);
strActionXPath = "/Actions/Action[checkbox='" + strChkID + "']/*self::Name]";
strAction = getCyleXML.SelectSingleNode(strActionXPath).ToString();
actionArray.Add(strAction);
}
}
// Now we need to call itself (recursion) because all items (Panel, GroupBox, etc) is a container so we need to check
// all containers for any checkboxes.
if (c.HasControls())
{
checkBoxValidation(c, strKey, actionArray);
}
}
return actionArray;
}
How do we pass the Click event of ImageButton inside a GridView to httpmodule
for linkbutton's i am doing this way:
if (request.Form.GetValues("__EVENTTARGET") != null)
{
//If it's a link button execute we can directley check for the params
if (request.Params.Get("__EVENTTARGET").Contains("xyz"))
{
//some Code
}
This is not working for ImageButton.
If you're trying to attach an event to a button within a gridview might I suggest in your base page on the prerender event parse through all gridviews on the page (use a recursive findcontrol algorithm) and look for any imagebuttons, if you find one you should then be able to attach an event to it.
EDIT:
I use something similar in the following:
public abstract class AmendmentPopUpWindow : BaseMasterPlanPage
{
// override this method if the correct save controls arent being hidden in the popups
public virtual IEnumerable<WebControl> SaveControls
{
get { return Controls.All().OfType<WebControl>().Where(c => c.ID.ToLower().Contains("save")); }
}
protected override void OnPreRender(EventArgs e)
{
if (WebConfiguration.Global_EnableAmendments && SystemVersion.HasValue)
{
foreach (var control in Controls.All())
{
if (control is RadioButton || control is TextBox || control is DropDownList || control is RadComboBox || control is CheckBox || control is CheckBoxList ||
control is RadEditor || control is RadTextBox || control is RadNumericTextBox)
{
var webControl = control as WebControl;
webControl.Enabled = false;
webControl.ForeColor = Color.Gray;
}
}
foreach (var saveControl in SaveControls)
saveControl.Visible = false;
}
base.OnPreRender(e);
}
EDIT: The .All() is an extension method defined as follows (stolen from here)
public static IEnumerable<Control> All(this ControlCollection controls)
{
foreach (Control control in controls)
{
foreach (Control grandChild in control.Controls.All())
yield return grandChild;
yield return control;
}
}
ImageButtons have an additional quasi-property in their names which identifies the mouse-coordinates (X and Y).
So to find the ImageButton's name your should iterate through posted parameters and found those which end with .x or .y:
foreach (string item in request.Form)
{
if (item.EndsWith(".x") || item.EndsWith(".y"))
{
var controlName = item.Substring(0, item.Length - 2);
// some code here
}
}
You could also cound this answer useful. It contains a more generic method to determine which control caused a postback.
I am developing a sharepoint 2007 web part that uses custom properties. Here is one:
[Personalizable(PersonalizationScope.User), WebDisplayName("Policy Update List Name")]
[WebDescription("The name of the SharePoint List that records all the policy updates.\n Default value is Policy Updates Record.")]
public string PolicyUpdateLogName
{
get { return _PolicyUpdateLogName == null ? "Policy Updates Record" : _PolicyUpdateLogName; }
set { _PolicyUpdateLogName = value; }
}
The properties work fine except that the changes are not reflected in the web part until you leave the page and navigate back (or just click on the home page link). Simply refreshing the page doesn't work, which makes me think it has something to do with PostBacks.
My current theory is that the ViewState is not loading postback data early enough for the changes to take effect. At the very least, the ViewState is involved somehow with the issue.
Thanks,
Michael
Here is more relevant code:
protected override void CreateChildControls()
{
InitGlobalVariables();
FetchPolicyUpdateLog_SPList();
// This function returns true if the settings are formatted correctly
if (CheckWebPartSettingsIntegrity())
{
InitListBoxControls();
InitLayoutTable();
this.Controls.Add(layoutTable);
LoadPoliciesListBox();
}
base.CreateChildControls();
}
...
protected void InitGlobalVariables()
{
this.Title = "Employee Activity Tracker for " + PolicyUpdateLogName;
policyColumnHeader = new Literal();
confirmedColumnHeader = new Literal();
pendingColumnHeader = new Literal();
employeesForPolicy = new List<SPUser>();
confirmedEmployees = new List<SPUser>();
pendingEmployees = new List<SPUser>();
}
...
// uses the PolicyUpdateLogName custom property to load that List from Sharepoint
private void FetchPolicyUpdateLog_SPList()
{
site = new SPSite(siteURL);
policyUpdateLog_SPList = site.OpenWeb().GetList("/Lists/" + PolicyUpdateLogName);
}
...
protected void InitListBoxControls()
{
// Init ListBoxes
policies_ListBox = new ListBox(); // This box stores the policies from the List we loaded from SharePoint
confirmedEmployees_ListBox = new ListBox();
pendingEmployees_ListBox = new ListBox();
// Postback & ViewState
policies_ListBox.AutoPostBack = true;
policies_ListBox.SelectedIndexChanged += new EventHandler(OnSelectedPolicyChanged);
confirmedEmployees_ListBox.EnableViewState = false;
pendingEmployees_ListBox.EnableViewState = false;
}
...
private void LoadPoliciesListBox()
{
foreach (SPListItem policyUpdate in policyUpdateLog_SPList.Items)
{
// Checking for duplicates before adding.
bool itemExists = false;
foreach (ListItem item in policies_ListBox.Items)
if (item.Text.Equals(policyUpdate.Title))
{
itemExists = true;
break;
}
if (!itemExists)
policies_ListBox.Items.Add(new ListItem(policyUpdate.Title));
}
}
Do some reading up on the Sharepoint web part life cycle. Properties are not updated until the OnPreRender event.
Perhaps my previous question on output caching output caching was too complex.
Let's simplify.
How can I get the final, "ready for sending" rendered HTML from a page (or control) event in ASP.Net? I assume that this will be the same content that will be used for the output cache, so could be queried to find out what is about to be placed into the cache.
Code copied from:
http://aspcode.net/Last-second-HTML-changes-in-your-ASPNET-page.aspx
protected override void Render(HtmlTextWriter writer)
{
using(System.IO.MemoryStream msOur = new System.IO.MemoryStream())
{
using(System.IO.StreamWriter swOur = new System.IO.StreamWriter(msOur))
{
HtmlTextWriter ourWriter = new HtmlTextWriter(swOur);
base.Render(ourWriter);
ourWriter.Flush();
msOur.Position = 0;
using(System.IO.StreamReader oReader = new System.IO.StreamReader(msOur))
{
string sTxt = oReader.ReadToEnd();
Response.Write(sTxt);
oReader.Close();
}
}
}
}
HTML has an input button type to reset all fields in a form to their initial state in one step: <input type="reset" ... />.
Is there a similar simple way to reset all form fields of an aspx page from code-behind? Or is it necessary to reset all controls one by one with TextBox1.Text=string.Empty, TextBox2.Text=string.Empty, etc. ?
Thanks in advance!
Update:
Context is a simple Contact/"Send us a message" page with 8 asp:TextBoxes on the page (where the user enters the name, address, phone, email, message, etc.). Then he clicks on submit, the Onclick message handler in code-behind sends an email to some administrator, and all the form fields the user filled in should be emptied and he gets a notification in a label ("Message sent blabla..."). I want to have the form fields cleared to avoid that the user clicks again on submit and the same message is sent a second time.
You need only write a fork for each type of control unless one of the control has something special that needs to be done to reset it.
foreach( var control in this.Controls )
{
var textbox = control as TextBox;
if (textbox != null)
textbox.Text = string.Empty;
var dropDownList = control as DropDownList;
if (dropDownList != null)
dropDownList.SelectedIndex = 0;
...
}
ADDITION You asked how to clear controls even ones that are buried. To do that, you should create a recursive routine like so:
private void ClearControl( Control control )
{
var textbox = control as TextBox;
if (textbox != null)
textbox.Text = string.Empty;
var dropDownList = control as DropDownList;
if (dropDownList != null)
dropDownList.SelectedIndex = 0;
...
foreach( Control childControl in control.Controls )
{
ClearControl( childControl );
}
}
So, you would call this by passing the page:
ClearControls( this );
Refer this link for more information
http://www.freshcodehub.com/Article/3/clear-all-fields-like-textbox-dropdownlist-checkbox-radiobutton-label-after-form-submission-in-aspnet-c
public void ClearControls(Control parent)
{
foreach (Control c in parent.Controls)
{
if ((c.GetType() == typeof(TextBox))) //Clear TextBox
{
((TextBox)(c)).Text = "";
}
if ((c.GetType() == typeof(DropDownList))) //Clear DropDownList
{
((DropDownList)(c)).ClearSelection();
}
if ((c.GetType() == typeof(CheckBox))) //Clear CheckBox
{
((CheckBox)(c)).Checked = false;
}
if ((c.GetType() == typeof(CheckBoxList))) //Clear CheckBoxList
{
((CheckBoxList)(c)).ClearSelection();
}
if ((c.GetType() == typeof(RadioButton))) //Clear RadioButton
{
((RadioButton)(c)).Checked = false;
}
if ((c.GetType() == typeof(RadioButtonList))) //Clear RadioButtonList
{
((RadioButtonList)(c)).ClearSelection();
}
if ((c.GetType() == typeof(HiddenField))) //Clear HiddenField
{
((HiddenField)(c)).Value = "";
}
if ((c.GetType() == typeof(Label))) //Clear Label
{
((Label)(c)).Text = "";
}
if (c.HasControls())
{
ClearControls(c);
}
}
}
using the manual approach of String.Empty for each and every Textbox or any other field will be cumbersome, also by using Response.Redirect(); it will be difficult to show any confirmation message or same. So, on reading so many blogs i have found a reliable approach so far:
Public void reset(Control control)
{
foreach (Control x in control.Controls)
{
if (x is TextBox)
{
(x as TextBox).Text = String.Empty;
}
else if (x is DropDownList)
{
(x as DropDownList).SelectedIndex = 0;
}
.
.
reset(x);
}
}
use this code as reset(this); in your page wherever you want to reset or clear the values. At end of the if conditions do not forget to use the function recursively using the same
`Control` object x.
Using form.Controls.Clear() is not such a good approach because it will clear the entire form and you will even lose all the buttons on the form.
Instead if you just want to clear all the form fields like text fields and radio buttons I would recommend you try the following:
If you have a Reset button “Button1” then on click call a function reset();
In the reset function:
protected void resetButton_Click(object sender, EventArgs e)
{
TextBox1.Text=""; //set equal to empty string to all fields
}
Or redirect to same page by terminating the previous page
protected void resetButton_Click(object sender, EventArgs e)
{
Response.Redirect("~/Test2.aspx", true);
}
For your scenario the easiest way to clear the fields, in my opinion, is to turn off the ViewState (EnableViewState=false) of the controls you want to appear blank after the submit.
Or perhaps for the whole page unless there is some state you need.