Tuesday 24 May 2016
Razor - C# Loops and Arrays
For Loops
If you need to run the same statements repeatedly, you can program a loop.
If you know how many times you want to loop, you can use a for loop. This kind of loop is especially useful for counting up or counting down:
<html>
<body>
@for(var i = 10; i < 21; i++)
{<p>Line @i</p>}</body>
</html>
<body>
@for(var i = 10; i < 21; i++)
{<p>Line @i</p>}</body>
</html>
For Each Loops
If you work with a collection or an array, you often use a for each loop.
A collection is a group of similar objects, and the for each loop lets you carry out a task on each item. The for each loop walks through a collection until it is finished.
The example below walks through the ASP.NET Request.ServerVariables collection.
<html>
<body>
<ul>
@foreach (var x in Request.ServerVariables)
{<li>@x</li>}</ul>
</body>
</html>
<body>
<ul>
@foreach (var x in Request.ServerVariables)
{<li>@x</li>}</ul>
</body>
</html>
While Loops
The while loop is a general purpose loop.
A while loop begins with the while keyword, followed by parentheses, where you specify how long the loop continues, then a block to repeat.
While loops typically add to, or subtract from, a variable used for counting.
In the example below, the += operator adds 1 to the variable i, each time the loop runs.
<html>
<body>
@{
var i = 0;
while (i < 5)
{
i += 1;
<p>Line @i</p>
}
}
</body>
</html>
<body>
@{
var i = 0;
while (i < 5)
{
i += 1;
<p>Line @i</p>
}
}
</body>
</html>
Arrays
An array is useful when you want to store similar variables but don't want to create a separate variable for each of them:
@{
string[] members = {"Jani", "Hege", "Kai", "Jim"};
int i = Array.IndexOf(members, "Kai")+1;
int len = members.Length;
string x = members[2-1];
}<html>
<body>
<h3>Members</h3>
@foreach (var person in members)
{
<p>@person</p>
}
<p>The number of names in Members are @len</p>
<p>The person at position 2 is @x</p>
<p>Kai is now in position @i</p>
</body>
</html>
string[] members = {"Jani", "Hege", "Kai", "Jim"};
int i = Array.IndexOf(members, "Kai")+1;
int len = members.Length;
string x = members[2-1];
}<html>
<body>
<h3>Members</h3>
@foreach (var person in members)
{
<p>@person</p>
}
<p>The number of names in Members are @len</p>
<p>The person at position 2 is @x</p>
<p>Kai is now in position @i</p>
</body>
</html>
Difference between ListView and GridView
ListView
GridView
It was introduced with Asp.Net 3.5.
It was introduced with Asp.Net 2.0.
Template driven.
Rendered as Table.
Built-in supports for Data grouping.
Need to write custom code.
Built-in supports for Insert operation.
Need to write custom code.
Provides flexible layout to your data.
Need to write custom code.
Performance is fast is compared to GridView.
Performance is slow as compared to ListView.
Difference Between GridView and DataGrid and ListView
GridView
DataGrid
It was introduced with Asp.Net 2.0.
It was introduced with Asp.Net 1.0.
Built-in supports for Paging and Sorting.
For sorting you need to handle SortCommand event and rebind grid required and for paging you need to handle the PageIndexChanged event and rebind grid required.
Built-in supports for Update and Delete operations.
Need to write code for implementing Update and Delete operations.
Supports auto format or style features.
This features is not supported.
Performance is slow as compared to DataGrid
Performance is fast as compared to GridView.
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