6. Delegates

A delegate is a reference to a function (single cast delegate) or to multiple functions (multi cast delegate)

Here's the implementation of a multi cast delegate:

//1. Declaration
public delegate void MyDelagate(int a, int b); 
public class Example
{
 // methods to be assigned and called by delegate
 public void Sum(int a, int b)
 {
 Console.WriteLine("Sum of integers is = " + (a + b));
 }
 
 public void Difference(int a, int b)
 {
 Console.WriteLine("Difference of integer is = " + (a - b));
 }
}
class Program
{
 static void Main()
 {
 Example obj = new Example();
 // 2. Instantiation
 MyDelagate multicastdel = new MyDelagate(obj.Sum); 
 multicastdel += new MyDelagate(obj.Difference);
 
 // 3. Invocation
 multicastdel (50, 20);
 }
}
 
/* Out put
 
 Sum of integers is = 70 
 Difference of integer is = 30
 
*/

5. Law of Demeter

"Don't talk to strangers". It's the simple explanation of the Demeter's Law.


It's also known as the "Law of train wrecks"
A -> B -> C

A should only know about it's closest "friends". It shouldn't access something from C. Instead, it should tell B to DO something, not to ask B about C.

TELL, DON'T ASK

A method M of an object O may only call the methods/params of the following:

1. O itself
2. M's parameters
3. Any object CREATED within M
4. O's direct component objects (O's instance variables)

Example:

public void ShowBallance(BankAccount account)
{
    Money amount = account.GetBallance();
    this.PrintToScreen(amount.PrintFormat());
}

This violates the low, because it can be written like:
this.PrintToScreen(account.GetBallance().PrintFormat()); // it's an obvious violation

Code should be:

public void ShowBallance(BankAccount account)

{
  account.PrintBallance(); // TELL, DON'T ASK!
}
  

4. Extension Methods

Extension Method = static method of a static class that can be invoked by using the instance method syntax.


e.g.:

public static class MyAwesomeExtensions
{
       public static int WordCount(this string input)
       {
           return input.Split(' ').Count();
       }
 
 
       public static string Concatenate(this string input, string toAdd)
       {
           return input + toAdd;
       }
 
       public static bool IsNullOrEmpty(this string s)
       {
           return string.IsNullOrEmpty(s);
       }
}

Then, you can use (in the same project or in a project referencing this class):

string s = "This is a test";

int wordCount = s.WordCount();

var something = s.Concatenate(" yeah");


The first parameter of the function, the one with the "this" keyword, specifies what type are you extending.

More on Extension Methods - MSDN

3. How to get PDF directly from the Report Server (SSRS)

C#:

            var user = ConfigurationManager.AppSettings["SsrsUsername"];
            var pass = ConfigurationManager.AppSettings["SsrsPassword"];
            var domain = ConfigurationManager.AppSettings["SsrsDomain"];
            var reportUrl = ConfigurationManager.AppSettings["SsrsReportUrl"];
            var credentials = new NetworkCredential(user, pass, domain);
            var webClient = new WebClient { Credentials = credentials };
            reportUrl = string.Format(reportUrl, id);
            return this.File(webClient.DownloadData(reportUrl), "application/pdf");


WebConfig:

    <add key="SsrsUsername" value="username" />
    <add key="SsrsPassword" value="password" />
    <add key="SsrsDomain" value="DOMAIN" />
    <add key="SsrsReportUrl" value="http://192.168.1.something/ReportServer?/Folder/ReportName&amp;rs:Command=Render&amp;rs:format=PDF&amp;SomeParameter={0}"

2. How to fill a div with an ajax call?

1. By using Ajax.BeginForm
 

using (Ajax.BeginForm("NavigatePage", "Case", null, new AjaxOptions {  

InsertionMode = InsertionMode.Replace, 

 UpdateTargetId = "caseList",  

HttpMethod = "POST" }, new { @role = "form" }))

2. By using jQuery

<script type="text/javascript"> $(document).ready(function () { $('.caseListTable tbody tr').click(function () { var caseNumber = $(this).children(":first").text(); var url = "@Html.Raw(Url.Action("GetCaseDetails"))" + "?caseNumber=" + caseNumber; $.get(url, function(data) { $("#caseDetails").html(data); }); }); }); </script>

1. Enable Ajax in ASP.NET MVC 5

In ASP.NET MVC5, Ajax is not enabled by default so Ajax.BeginForm won't work.

• Manage NuGet Packages > Install Microsoft jQuery UnobtrusiveAjax
• In BundleConfig.cs Add:

bundles.Add(new ScriptBundle("~/bundles/jqueryajax").Include(
                "~/Scripts/jquery.unobtrusive*"));

• In _Layout.cshtml add:

@Scripts.Render("~/bundles/jqueryajax")

That's it :)