SharePoint 2010 Blog: JavaScript

Retrieving Query String Value Through JavaScript

In World Wide Web, a query string is a part of a URL that contains data to be passed to web applications (http://en.wikipedia.org/wiki/Query_string).
The query string is composed of a series of field – value pair. Below is the pattern of query string:
field1=value1&field2=value2&field3=value3

An URL that contains query string can be depicted as follow:
http://test.com/tag?name=alma&role=user
The URL and query string separated by a question mark (?). Query string consist of two parts (field and value), and each of pair separated by ampersand (&). So the example above consists of two query strings which are name and type with value of each field ‘alma’ and ‘user’ respectively.

We can retrieve the query string values programmatically and used that values. Now we will learn how to get the query string values in ASP.NET and Javascript.

Retrieving Query Strings in ASP.NET
Retrieving query strings in ASP.NET is quite simple, what we need is just the following line of code:
Page.Request.QueryString[queryStringField];
or
Page.Request.QueryString[indexOfQueryString];

So If we need to retrieve the value of name field from this URL: http://test.com/tag?name=alma&role=user
Just do this inside of your ASP.NET code: Page.Request.QueryString["name"] or Page.Request.QueryString[0]. Lets look at how it work in simple source of code (Test.aspx):

<%@ Page Language=”C#” %>
<html>
<head>
<title>Query Strings in ASP.NET: Page 1</title>
<script language=”C#” runat=”server”>
void GetQrStr(object sender, EventArgs e)
{
// change the Response.Redirect parameter with your own location.
Page.Response.Redirect(“/…/Test2.aspx?name=alma&role=user”);
}
</script>
</head>
<body>
<form runat=”server”>
<asp:Button id=”btn” onclick=”GetQrStr” text=”Test Query Strings” runat=”server” />
</form>
</body>
</html>

Test.aspx will produce a button that will redirect to Test2.aspx when it clicked. This is code for Test2.aspx:

<%@ Page Language=”C#”%>

<html>
<head>
<title>Query Strings in ASP.NET: Page 2</title>
<script language=”C#” runat=”server”>
</script>
</head>
<body>
<%
// retrieves query string values
string name = Page.Request.QueryString["name"];
string role = Page.Request.QueryString["role"];

Page.Response.Write(“<h1>Name: “+name+”, Role: “+role+”</h1>”);
%>
</body>
</html>

In Test2.aspx we can get the values of ‘name’ and ‘role’ query strings then use both values as we need.

Retrieving Query Strings in Javascript
Javascript can be used for retrieves query string values too. We need the following code to get query string pairs (field & value) using Javascript:
window.location.search

The above code will return string started with ampersand in the URL (ampersand included). So if we run the above code against the following URL:http://localhost:8088/postings/QrStr/testjs2.htm?name=alma&role=user
The return value is ?name=alma&role=user

To understand the concept better I have write two simple HTML pages that show how to get query string values using Javascript. This is the first file (testqrstr.htm):

<html>
<head>
<title>Test Query Strings: Page 1</title>
<script lang=”javascript” type=”text/javascript”>
function testQueryStrings()
{
// change the window.location with your own.
window.location = “/…/testjs2.htm?name=alma&role=user”;
}
</script>
</head>
<body>
<input type=”button” id=”btn” value=”Test Query Strings” onclick=”testQueryStrings()” />
</body>
</html>

The output produced by testjs.htm is similar like the output of Test.aspx, when we click the button it will bring us to testjs2.htm (of course with the specified query strings!). Here testjs.htm:

<html>

<head>

<title>Test Query Strings: Page 2</title>

<script lang=”javascript” type=”text/javascript”>

var qrStr = window.location.search;

var spQrStr = qrStr.substring(1);

var arrQrStr = new Array();

// splits each of pair

var arr = spQrStr.split(’&’);

for (var i=0;i<arr.length;i++){

// splits each of field-value pair

var index = arr[i].indexOf(’=');

var key = arr[i].substring(0,index);

var val = arr[i].substring(index+1);

// saves each of field-value pair in an array variable

arrQrStr[key] = val;

}

alert(arrQrStr["Location"]);

</script>

</head>

<body>

</body>

</html>

Calling ASP.Net validators from JavaScript

There are situations when we want to call Asp.net validatiors form JavaScript. One such situation is when we want to close a pop up window on button click using window.close(). But before closing the window using JavaScript, we want to validate the data written in the controls of the window.

It possible to call Asp.net validators from JavaScript. The following code shows a portion of asp.net page which includes one standard .net required field validator and one regular expression validator.

<table>

<tr>

</tr>

<tr>

</tr>

</table>

In design mode, it looks as below

View in design mode

Now we want to make sure that .net validators get fired up on “Submit” button click before closing the window using javascript window.close(). In our example, we have a text box where we expect a single digit before closing the window.

All we have to do to fire up .net validators is to call “Page_ClientValidate()” function. The following JavaScript code shows how “Page_ClientValidate()” function can be used before closeing window.

function performCheck()
{

if(Page_ClientValidate())
{

window.close();

}

}
</script>

Now, if the Submit button is clicked leaving the text box empty, the required field validator will fire up as shown in the below screen shot.

Required field validotor fires up

If any thing is written in other than a single digit, we will get the following output.

Regular Expression Validator fires up

How about Calling any specific validator rather than all?

Well, this can be done as well. In this case we need to provide a ValidationGroup name for the validator and pass the validator group name to Page_ClientValidate() function as parameter. The following code segment shows a group name is provided for the required field validator and passed it to

Page_ClientValidate() function. In this case, only required field validatior will be fired up and not the regular expression validator.

<table>

<tr>

</tr>

<tr>

</tr>

</table>

if(Page_ClientValidate(“Required”))
{

window.close();

}

}
</script>

Advantage

By using standard asp.net validators for validation, we don’t have to write JavaScript code to do the validation. This can minimize the development time to a great extent.

Considerations while making a control invisible

If we want to make a control invisible in asp.net, may be the most straight forward way is to set the Visible property to “false”. As long as we are accessing this control from server side, there is no problem. However, if we need to access it from client side using JavaScript, then we have a problem. Once we make the control invisible by setting the Visible property to “false”, we will no longer be able to access it from client side using JavaScript and we will not find the control using document.getElementById(“controlID”).

Solution to this problem is to use the style property to make it invisible. Here are some considerations as well. By using style, we can make a control invisible in two ways.

using visibility:hidden
using display:none

By using any one of the above 2 ways we can still access a control by using document.getElementById(“controlID”) but if we use visibility:hidden, the control will still occupy the space. On the other hand, the control will not occupy space if “display:none” is used.

Making a button coltrol invisible using style

To make a control invisible from aspx page the following code can be used

Setting display style from aspx page

To make a control invisible from cs page the following code can be used

setting display style from cs file

SharePoint 2010 Blog

Tuesday, 18 February 2014

JavaScript

Retrieving Query String Value Through JavaScript

Calling ASP.Net validators from JavaScript

Considerations while making a control invisible

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