Conditionally add a control on Markup during Databinding

There are cases that we want to add a control conditionally if the field agrees on some condition. This is common on dataaware controls were we present our data. I come accross with this problem where I need to render a Hyperlink button when HistoryId is not null in the database. We usually write the code to bind controls like as follows:

<asp:LinkButton CommandName = '<%#
string.Format("History{0}",Eval("CustomerHistoryId")) %>' runat= "server"
OnClick= "ViewCustomerHistory"> View ... </asp:LinkButton>

The following code above will just add linkbutton controls on all records fetch, but this is not the desired output. What I did is to use tertiary operator and set the style to none if HistoryId is null. The code below shows how I did it:

<asp:LinkButton CommandName = '<%#
string.Format("History{0}",Eval("CustomerHistoryId")) %>' runat= "server"
Style ='<%# Eval("CustomerHistoryId").ToString() == "" ? "Display:None"
: "Display:Inline"%>'
OnClick= "ViewCustomerHistory"> View ...
</asp:LinkButton>

using JSON in C#.Net

I never thought that my objects can be accessed in javascript until I discover JSON. JSON or Javascript Object Notation is a simple data transformation from your serverside objects to clientside scripting.
A string like

'person = {"firstName": "Brett", "lastName":"McLaughlin", "email":
"brett@newInstance.com" } '

can be deserialized into JSON object using eval. Then can be accessed as simple as person.firstName. Below is a sample javascript code:

var myJSON = 'person = {"firstName": "Brett", "lastName":"McLaughlin",
"email": "brett@newInstance.com" } ' ;
eval(myJSON);
alert(person.firsName + ' ' + person.lastName + ', ' + person.email);

the code above will give a pop-up message saying:

Brett McLaughlin, brett@newInstance.com

Now how can we create a JSON object in C#.net and be able to pass it on clientside? Here is the procedure:

1. Create a struct to be serialized as JSON:

public struct person
{
public string firstName;
public string lastName;
public string email;
}

2. Create a method that will return a serialized JSON object

public string SerializedJSON(object toSerialize, string className)
{
System.Web.Script.Serialization.JavaScriptSerializer jss;
jss = new System.Web.Script.Serialization.JavaScriptSerializer();
objectSystem.Text.StringBuilder sbControls = new
System.Text.StringBuilder();
jss.Serialize(toSerialize, sbControls);
return className + "=" + sbControls.ToString();
}

3. then register the clientside method to call with parameter as JSON serialized string. This may be an attributes of controls event or a a method call on clientside

//as attribute
string serialized = SerializedJSON(person, "person");
button1.Attributes.add("onClick",
"parseJSON('"+ serialized +"')");
//as method call on serverside

ScriptManager.RegisterClientScriptBlock(this,this.GetType(),
"JS
Method Call","parseJSON('"+ serialized +"')", true);

4. Now with those server side code, here is how we do the clientside:

function parseJSON(serializedJSON)
{
eval(serializedJSON);
alert(person.firsName + ' ' + person.lastName + ', ' +
person.email);
}

You can even use JSON on array of objects and be able to call it by index on clientside like

person[0].firstName;
or
person[1].firstName;

I usually use list<object> then serialize it to JSON. And there are many things to explore on JSON and that is what I'm doing right now! Thanks JSON!

links: http://www-128.ibm.com/developerworks/web/library/wa-ajaxintro10/

Adding Javascript file programmatically in C#

Just got it from ASP.Net Forum and found it very useful for me. Thanks to NC01!!

string resourceName = "YourJavaScriptFile.js";
if ( !this.Page.IsClientScriptBlockRegistered(resourceName) )
{
// If the file is on the server root:
// Ex: http://localhost/YourJavaScriptFile.js
string filePath = System.Web.HttpContext.Current.Request.Url. GetLeftPart( UriPartial.Authority) + "\\" + resourceName;
// If the file is on the app virtual root:
// Ex: C:/Inetpub/wwwroot/Test/YourJavaScriptFile.js
string filePath = System.AppDomain.CurrentDomain.BaseDirectory + resourceName;
// If the file is in a sub-folder inside of the app virtual root:
// Ex: C:/Inetpub/wwwroot/Test/ScriptFiles/YourJavaScriptFile.js
string filePath = System.AppDomain.CurrentDomain.BaseDirectory + "ScriptFiles/" + resourceName;
string scriptText = string.Format( System.Globalization.CultureInfo.InvariantCulture, "\n<script type='text/JavaScript' src='{0}'></script>\n", filePath);
this.Page.RegisterClientScriptBlock(resourceName, scriptText);
}

Note that RegisterOnSubmitStatement, RegisterStartupScript, RegisterClientScriptBlock, etc have changed since version 1.1 and you will get a compiler warning with the above. See http://msdn2.microsoft.com/en-us/library/system.web.ui.clientscriptmanager.aspx for more info.

I just highlighted the property of getting the BaseURL, System.AppDomain.CurrentDomain.BaseDirectory , i've been looking for it before and finally I got an answer. What I do before is put my baseURL in web.Config, but everytime I deploy it on different test site I have to change the value on web.config before publishing.

Selecting specific Row and Size in a record using ROW_NUMBER()

Sometime we want to select row that is between a record like for example record 10 to 20. We cannot achieve that by using TOP for it will just get the records starting from top. We can write it like this:
SELECT TOP 20 * FROM TABLE1 WHERE FIELDID NOT IN (SELECT TOP 10 FIELDID FROM TABLE1)
But performance wise this is not advisable. I recommend using ROW_NUMBER() OVER function in MSSQL to assign ROWID from the table then selecting the ROW in where clause. Here is the syntax below:

SELECT * FROM ( SELECT *, ROW_NUMBER() OVER (ORDER BY OrderField) as row FROM Table1) a WHERE row > (@RecordNo-1) and row <= (@RecordNo + @RecordSize-1)

where:
@RecordNo is the starting row
@RecordSize is the no of rows you want to retrieve starting from @RecordNo
OrderField is the order you want for the record before extraction

So to select records 10 to 20 you write it as:

SELECT * FROM ( SELECT *, ROW_NUMBER() OVER (ORDER BY OrderField) as row FROM Table1) a WHERE row > (9) and row <= (19)

Adding triggers for your Table

Triggers are very useful specially on registering audits on changes on tables.
Triggers has INSERTED and DELETED object that can be used to get the activity
made on the table and be able to save it on your audit tables.
These objects has the same schema as your table so you can join it with other table to get other information you needed

Below is the syntax in adding trigger on your table and how to save it on your audit.

CREATE TRIGGER [Trigger_all] ON [dbo].[SampleTable]
For INSERT, UPDATE, DELETE
AS
IF EXISTS(SELECT * FROM INSERTED) AND EXISTS(SELECT * FROM DELETED)
BEGIN
--procedure for Update
INSERT INTO SampleTable_Audit VALUES(SELECT *, 'EDITTED', timestamp() FROM DELETED)
END
ELSE IF EXISTS(SELECT * FROM INSERTED)
BEGIN
--Procedure for insert
INSERT INTO SampleTable_Audit VALUES(SELECT *, 'Inserted', timestamp() FROM INSERTED)
END

ELSE IF EXISTS(SELECT * FROM DELETED)
BEGIN
--Procedure for delete
INSERT INTO SampleTable_Audit VALUES(SELECT *, 'EDITTED', timestamp() FROM DELETED)
END

Calling Server Side Method with postback in C#

I've been researching for how to call server side methods over the internet but has been frustrated for all I searched was calling server side method without postback using pagemethods or using the ICallBackEventHandler that works like webservice calls in AJAX. I've been pondering time to solve this and found a solutions for myself.

Here is how I did it:

• Create a linkbutton on design and write an event for this. This event will be called on client side by some javascript function.
• Register the Server Side Function by using the following:

StringBuilder jscript = new StringBuilder();
jsscript.append("function callServerEvent(){");
jsscript.append(ClientScript.GetPostBackEventReference (LinkButton1, "") + ";}");
RegisterClientScriptBlock("call server", jsscript.ToString());

• Do this on Page_Load event, then you can now call callServerEvent() from javascript will do a post back and update controls.
• To hide the control on rendering the page set the display:none on LinkButon's style.
  

I usually use this in calling server
side function to update controls inside my updatepanel. Using Pagemethods are used for calling static methods and using ICallBackEventHandler is for calling serverside method but with no postback at all.

Selecting the last record entered on audit trail for each Item

Here is another trick I love and was amazed of what I have achieved!
Audit trail accumulates all activities happened on the system or movements happened on the item. It is not that easy to extract from the audit trail the last movement of all the items, unless you individually query on each item and get the max date then transfer it to another table, a temporary maybe, then go to the next item and repeat the process until you have the last item. But I found a way to query it on just a single query string:

SELECT A.ProductID, B.Description,
LTRIM(RIGHT(MAX(CONVERT(VARCHAR(19), A.AuditTime, 120) +
RIGHT(REPLICATE(' ',100) + Activity,100)),100)) AS LastActivity FROM AuditTrail A INNER JOIN Products B ON A.ProductID= B.ProductID GROUP BY A.ProductID, B.Description

Here is how this works:

1. Convert the Audit Time to YYYY-MM-DD HH:NN:SS format, this will ensure the order of activities according to time it was written.
2. RIGHT(REPLICATE(' ',100) + Activity,100)) This will put leading spaces on activity to make the string a 100 character. eg. '10 items sold' will become ' 10 items sold' with 87 leading spaces.
3. Concatenate the 19 character datetime to the 100 character Activity making it a sum of 119 characters
4. Get the MAX value of the 119 character field that we have created. This will get the Max value we want since it will be alphabetically arranged.
5. Now its time to remove the date and time that we don't want to appear then trim again the leading spaces we added. this is the function of LTRIM(RIGHT( ---,100)) where the function right gets the 100 character activity we created ant LTRIM removes leading spaces.

Now thats it. We got the Activity of the last movement for each product.