Updating property value in a custom contorl using ASP.NET 2.0 Callback

A

Alani

Hello All,

I'm a new ASP.NET programmer and I want to create a custom control
consist of two properties (Number1) and (Number2) and both of them are
integers and default value = 0,

now I'm using callback technique so I can change those two proprties
via ChangeNumber1 and ChangeNumber2 functions.

what happens is that when I change the Number1 for to number and get
the result of the callback event and trying to change the second number
I always get the default value of Number1 (which is 0) and always the
result return 0;

I know that I can pass the two new properties value via the callback
function but I want it works like this.

anybody can help ?

========================================================================
My Custom Contorl code is:
[ToolboxData("<{0}:MyCalculator runat=server></{0}:MyCalculator>")]
public class MyCalculator : WebControl, ICallbackEventHandler
{
private const int _number1Default = 0;
private const string _number1DefaultViewState = "Number1";

[Bindable(true)]
[DefaultValue(_number1Default)]
[Description("The first number")]
[Localizable(true)]
public int Number1
{
get
{
object obj = ViewState[_number1DefaultViewState];
return (obj != null) ? (int)obj : 0;
}
set
{
ViewState[_number1DefaultViewState] = value;
}
}

private const int _number2Default = 0;
private const string _number2DefaultViewState = "Number2";

[Bindable(true)]
[DefaultValue(_number2Default)]
[Description("The first number")]
[Localizable(true)]
public int Number2
{
get
{
object obj = ViewState[_number2DefaultViewState];
return (obj != null) ? (int)obj : 0;
}
set
{
ViewState[_number2DefaultViewState] = value;
}
}

protected override void OnPreRender(EventArgs e)
{
ClientScriptManager csm = this.Page.ClientScript;

{ // Number1 Script Register
String cbNumber1Ref = csm.GetCallbackEventReference(this,
"eventArgument",
"GetMultiplyResult", "context");

StringBuilder sbNumber1CallbackScript = new
StringBuilder();
sbNumber1CallbackScript.Append("\n");
sbNumber1CallbackScript.Append("function
ChangeNumber1(eventArgument, context)\n");
sbNumber1CallbackScript.Append("{\n");
sbNumber1CallbackScript.Append(" " + cbNumber1Ref);
sbNumber1CallbackScript.Append(";\n}");

// Register script blocks will perform call to the server.
if (!csm.IsClientScriptBlockRegistered(this.GetType(),
"OnChangeNumber1"))
{
csm.RegisterClientScriptBlock(this.GetType(),
"OnChangeNumber1",
sbNumber1CallbackScript.ToString(), true);
}
}

{ // Number2 Script Register
String cbNumber2Ref = csm.GetCallbackEventReference(this,
"eventArgument",
"GetMultiplyResult", "context");

StringBuilder sbNumber2CallbackScript = new
StringBuilder();
sbNumber2CallbackScript.Append("\n");
sbNumber2CallbackScript.Append("function
ChangeNumber2(eventArgument, context)\n");
sbNumber2CallbackScript.Append("{\n");
sbNumber2CallbackScript.Append(" " + cbNumber2Ref);
sbNumber2CallbackScript.Append(";\n}");

// Register script blocks will perform call to the server.
if (!csm.IsClientScriptBlockRegistered(this.GetType(),
"OnChangeNumber2"))
{
csm.RegisterClientScriptBlock(this.GetType(),
"OnChangeNumber2",
sbNumber2CallbackScript.ToString(), true);
}
}
}
public override void RenderControl(HtmlTextWriter writer)
{
writer.RenderBeginTag(HtmlTextWriterTag.B);
writer.Write("This is My Control");
writer.RenderEndTag();
}

private int _result;
void ICallbackEventHandler.RaiseCallbackEvent(string
eventArgument)
{
string[] args = eventArgument.Split(':');

switch (args[0])
{
case "Number1":
{
Number1 = int.Parse(args[1]);
}
break;

case "Number2":
{
Number2 = int.Parse(args[1]);
}
break;
}

_result = Number1 * Number2;
}

string ICallbackEventHandler.GetCallbackResult()
{
return _result.ToString();
}
}
========================================================================

And the page that uses it is:
========================================================================
<%@ Page Language="C#" AutoEventWireup="true"
CodeFile="Default.aspx.cs" Inherits="_Default" %>

<%@ Register Assembly="WebControlLibrary1"
Namespace="WebControlLibrary1" TagPrefix="cc1" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Untitled Page</title>
<script type="text/javascript">
function OnChangeNum1()
{
var cmb1 = document.getElementById("Select1");
ChangeNumber1(cmb1.selectedIndex);
}

function OnChangeNum2()
{
var cmb2 = document.getElementById("Select2");
ChangeNumber2(cmb2.selectedIndex);
}

function GetMultiplyResult(mulResult)
{
document.getElementById("Text1").value = mulResult;
}
</script>
<script src="ClientScript.js" type="text/javascript">
// <!CDATA[

// ]]>
</script>
</head>
<body>
<form id="form1" runat="server">
<div>
<br />
<strong>First Number &nbsp; &nbsp; :</strong> &nbsp;
<select id="Select1" onchange="OnChangeNum1()" style="width:
121px" onclick="return Select1_onclick()">
<option selected="selected">0</option>
<option>1</option>
<option>2</option>
<option>3</option>
</select>
<br />
<strong>Second Number:</strong> &nbsp;&nbsp;<select id="Select2"
onchange="OnChangeNum2()" style="width: 121px">
<option selected="selected">0</option>
<option>1</option>
<option>2</option>
<option>3</option>
</select><br />
<br />
<strong>Result:</strong>
<input id="Text1" type="text" style="width: 170px" /><br />
<br />
&nbsp;<cc1:MyCalculator ID="MyCalculator1" runat="server"
Width="257px" />
</div>
</form>
</body>
</html>
========================================================================

Thanks
Omar alani
 
G

Guest

Try saving the values to Session state instead of ViewState.
You see, ViewState is not being persisted because it normally gets rendered
along with the page but in the case of callbacks you are not re-rendering the
page.

--
I hope this helps,
Steve C. Orr
MCSD, MVP
http://Steve.Orr.net



Alani said:
Hello All,

I'm a new ASP.NET programmer and I want to create a custom control
consist of two properties (Number1) and (Number2) and both of them are
integers and default value = 0,

now I'm using callback technique so I can change those two proprties
via ChangeNumber1 and ChangeNumber2 functions.

what happens is that when I change the Number1 for to number and get
the result of the callback event and trying to change the second number
I always get the default value of Number1 (which is 0) and always the
result return 0;

I know that I can pass the two new properties value via the callback
function but I want it works like this.

anybody can help ?

========================================================================
My Custom Contorl code is:
[ToolboxData("<{0}:MyCalculator runat=server></{0}:MyCalculator>")]
public class MyCalculator : WebControl, ICallbackEventHandler
{
private const int _number1Default = 0;
private const string _number1DefaultViewState = "Number1";

[Bindable(true)]
[DefaultValue(_number1Default)]
[Description("The first number")]
[Localizable(true)]
public int Number1
{
get
{
object obj = ViewState[_number1DefaultViewState];
return (obj != null) ? (int)obj : 0;
}
set
{
ViewState[_number1DefaultViewState] = value;
}
}

private const int _number2Default = 0;
private const string _number2DefaultViewState = "Number2";

[Bindable(true)]
[DefaultValue(_number2Default)]
[Description("The first number")]
[Localizable(true)]
public int Number2
{
get
{
object obj = ViewState[_number2DefaultViewState];
return (obj != null) ? (int)obj : 0;
}
set
{
ViewState[_number2DefaultViewState] = value;
}
}

protected override void OnPreRender(EventArgs e)
{
ClientScriptManager csm = this.Page.ClientScript;

{ // Number1 Script Register
String cbNumber1Ref = csm.GetCallbackEventReference(this,
"eventArgument",
"GetMultiplyResult", "context");

StringBuilder sbNumber1CallbackScript = new
StringBuilder();
sbNumber1CallbackScript.Append("\n");
sbNumber1CallbackScript.Append("function
ChangeNumber1(eventArgument, context)\n");
sbNumber1CallbackScript.Append("{\n");
sbNumber1CallbackScript.Append(" " + cbNumber1Ref);
sbNumber1CallbackScript.Append(";\n}");

// Register script blocks will perform call to the server.
if (!csm.IsClientScriptBlockRegistered(this.GetType(),
"OnChangeNumber1"))
{
csm.RegisterClientScriptBlock(this.GetType(),
"OnChangeNumber1",
sbNumber1CallbackScript.ToString(), true);
}
}

{ // Number2 Script Register
String cbNumber2Ref = csm.GetCallbackEventReference(this,
"eventArgument",
"GetMultiplyResult", "context");

StringBuilder sbNumber2CallbackScript = new
StringBuilder();
sbNumber2CallbackScript.Append("\n");
sbNumber2CallbackScript.Append("function
ChangeNumber2(eventArgument, context)\n");
sbNumber2CallbackScript.Append("{\n");
sbNumber2CallbackScript.Append(" " + cbNumber2Ref);
sbNumber2CallbackScript.Append(";\n}");

// Register script blocks will perform call to the server.
if (!csm.IsClientScriptBlockRegistered(this.GetType(),
"OnChangeNumber2"))
{
csm.RegisterClientScriptBlock(this.GetType(),
"OnChangeNumber2",
sbNumber2CallbackScript.ToString(), true);
}
}
}
public override void RenderControl(HtmlTextWriter writer)
{
writer.RenderBeginTag(HtmlTextWriterTag.B);
writer.Write("This is My Control");
writer.RenderEndTag();
}

private int _result;
void ICallbackEventHandler.RaiseCallbackEvent(string
eventArgument)
{
string[] args = eventArgument.Split(':');

switch (args[0])
{
case "Number1":
{
Number1 = int.Parse(args[1]);
}
break;

case "Number2":
{
Number2 = int.Parse(args[1]);
}
break;
}

_result = Number1 * Number2;
}

string ICallbackEventHandler.GetCallbackResult()
{
return _result.ToString();
}
}
========================================================================

And the page that uses it is:
========================================================================
<%@ Page Language="C#" AutoEventWireup="true"
CodeFile="Default.aspx.cs" Inherits="_Default" %>

<%@ Register Assembly="WebControlLibrary1"
Namespace="WebControlLibrary1" TagPrefix="cc1" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Untitled Page</title>
<script type="text/javascript">
function OnChangeNum1()
{
var cmb1 = document.getElementById("Select1");
ChangeNumber1(cmb1.selectedIndex);
}

function OnChangeNum2()
{
var cmb2 = document.getElementById("Select2");
ChangeNumber2(cmb2.selectedIndex);
}

function GetMultiplyResult(mulResult)
{
document.getElementById("Text1").value = mulResult;
}
</script>
<script src="ClientScript.js" type="text/javascript">
// <!CDATA[

// ]]>
</script>
</head>
<body>
<form id="form1" runat="server">
<div>
<br />
<strong>First Number :</strong>
<select id="Select1" onchange="OnChangeNum1()" style="width:
121px" onclick="return Select1_onclick()">
<option selected="selected">0</option>
<option>1</option>
<option>2</option>
<option>3</option>
</select>
<br />
<strong>Second Number:</strong> <select id="Select2"
onchange="OnChangeNum2()" style="width: 121px">
<option selected="selected">0</option>
<option>1</option>
<option>2</option>
<option>3</option>
</select><br />
<br />
<strong>Result:</strong>
<input id="Text1" type="text" style="width: 170px" /><br />
<br />
<cc1:MyCalculator ID="MyCalculator1" runat="server"
Width="257px" />
</div>
</form>
</body>
</html>
========================================================================

Thanks
Omar alani
 
A

Alani

Thank you Steve for your reply.

your suggesstion worked correctly, BUT when I changed the class
declaration to add some initial value for the Number1 and Number2
properties, I got an exception because the Page.Session variable was
null in the set section of the property, I mean if I changed the class
declaration to be as follows:
=====================================================================================
[ToolboxData("<{0}:MyCalculator runat=server Number1=0
Number2=0></{0}:MyCalculator>")]

and change the property to be as follows:

[Bindable(true)]
[DefaultValue(_number1Default)]
[Description("The first number")]
[Localizable(true)]
public int Number1
{
get
{
object obj = null;
if (Page.Session != null)
{
//get a property unique name by adding the clientId for
this control to the original property name
string Number1ID = string.Format("{0}_Number1",
this.ClientID);
obj = Page.Session[Number1ID];
}
return (obj != null) ? (int)obj : 0;
}
set
{
if (Page.Session != null)
{
string Number1ID = string.Format("{0}_Number1",
this.ClientID);
Page.Session[Number1ID] = value;
}
}
}

=====================================================================================

Now, Is this what you mean or you meant something else ?

Is my code right or wrong ?

Thanks again,
Omar alani
 

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