Data Types define the type of data that a variable can store. Some variables store numbers, others store names. The built-in VB.NET type aliases and their equivalent .NET Framework types follow:
| VB Alias | .NET Type | Size | Range |
| SByte | System.SByte | 8 bits (1 byte) | -128 to 127 |
| Byte | System.Byte | 8 bits (1 byte) | 0 to 255 |
| Short | System.Int16 | 16 bits (2 bytes) | -32,768 to 32,767 |
| UShort | System.UInt16 | 16 bits (2 bytes) | 0 to 65,535 |
| Integer | System.Int32 | 32 bits (4 bytes) | -2,147,483,648 to 2,147,483,647 |
| UInteger | System.UInt32 | 32 bits (4 bytes) | 0 to 4,294,967,295 |
| Long | System.Int64 | 64 bits (8 bytes) | -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 |
| ULong | System.UInt64 | 64 bits (8 bytes) | 0 to 18,446,744,073,709,551,615 |
| VB Alias | .NET Type | Size | Precision | Range |
| Single | System.Single | 32 bits (4 bytes) | 7 digits | 1.5 x 10-45 to 3.4 x 1038 |
| Double | System.Double | 64 bits (8 bytes) | 15-16 digits | 5.0 x 10-324 to 1.7 x 10308 |
| Decimal | System.Decimal | 128 bits (16 bytes) | 28-29 decimal places | 1.0 x 10-28 to 7.9 x 1028 |
| VB Alias | .NET Type | Size (bits) | Range |
| Char | System.Char | 16 bits (2 bytes) | One Unicode symbol in the range of 0 to 65,535. |
| Boolean | System.Boolean | 32 bits (4 bytes) | True or False |
| Object | System.Object | 32/64 bits (4/8 bytes) | Platform dependent (a reference to an object). |
| Date | System.DateTime | 64 bits (8 bytes) | January 1, 0001 12:00:00 AM to December 31, 9999 11:59:59 PM |
| String | System.String | 80 + [16 * Length] bits (10 + [2 * Length] bytes) | A Unicode string with a maximum length of 2,147,483,647 characters. |
· All numeric data types
· Boolean, Char, and Date
· All structures, even if their members are reference types
· Enumerations, since their underlying type is always SByte, Short, Integer, Long, Byte, UShort, UInteger, orULong
· String
· All arrays, even if their elements are value types
· Class types, such as Form
· Delegates
· Namespaces
· Modules
· Events
· Properties and procedures
· Variables, constants, and fields
| Collections | Dynamic Array | Fast lookup | Required Cast | Good Choice for Booleans | Thread safety | Stores Any type object | Linear Array | Loop | Comments |
| List | Yes | Not good | No | No | no | No(Except List<object> ) | Yes | It is fast because it is Linear | |
| Dictionary | Yes | Yes | No | No | No | | | | |
| ArrayList | yes | No | Yes | No | No | Yes | Yes | | |
| Hashtable | | Yes | | | | | | | It is an older .NET Framework type. |
| ConcurrentDictionary | Yes | Yes | No | No | Yes | No | | | |
| ConcurrentBag | | | | | | | | | Sometimes lookup functionality is not required. ConcurrentBag allows us to safely Add and Take results |
| BitArray | | | | yes | | | | | The program creates a bool array with true and false values, and then the BitArray constructor converts those into one bit each. This means that instead of one byte for a bool, the values are stored as one bit, in one-eighth the space. |
| Tuple | | | | | | | | | A Tuple has many items. Each item can have any type. The Tuple class provides a unified syntax for creating objects with typed fields. |
| KeyValuePair | | | | | | | | | Tuple was faster in every test than KeyValuePair except in allocation performance. |
| Stack | | | | | | | | | |
| Queue | | | | | | | | | |
| HashSet | | | | | | | | | HashSet is an optimized set collection. It helps eliminates duplicate strings or elements in an array. It provides a simple syntax for taking the union of elements in a set. This is performed in its constructor. Constructor Example. This program contains a source array that contains several duplicated strings. It eliminates duplicate strings in the array. The program calls the HashSet constructor to transform the array elements into a set data structure. When the source input becomes large with thousands of elements, hashed collections are faster. |
| SortedSet | | | | | | | | | SortedSet is an ordered set collection. We have many elements and want to store them in a sorted order and also eliminate all duplicates from the data structure. The SortedSet is part of the System.Collections.Generic namespace. |
| Lazy | | | | | | | | | This type implements the lazy instantiation pattern. We look into the concept of thunks, as described in a programming textbook. The Lazy class has no relation to the Sleep method. |
| HybridDictionary | | | | | | | | | HybridDictionary attempts to optimize Hashtable. It implements a linked list and hash table data structure, switching over to the second from the first when the number of elements increases past a certain threshold. |
DECLARE @Search varchar(255)
SET @Search='COMPLETE'
SELECT DISTINCT
o.name AS Object_Name,o.type_desc,m.definition
FROM sys.sql_modules m
INNER JOIN sys.objects o ON m.object_id=o.object_id
WHERE m.definition Like '%'+@Search+'%'
ORDER BY 2,1
It's always better to generate a URL using “Url. Action” method to avoid URL issues. When Deploying application from one environment to other environments, it may not necessary to have a same website configuration on IIS. Means, On development you may have a virtual directory structure is “www.test.com/application/results” but in other environments, it configured as ““www.test.com/websitename/application/results” so we need to consider all these Directory structures when we are generating URL otherwise we run into issues. URL. Action method will take care of these things so it is a good idea to use URL. Action method to avoid URL issues
Example: Url.Action("results", "Application", new { id = Model.id })
Validations are very important in any application and Validations restrict the invalid data being entered into the application.
In MVC we can build a custom validations framework by extending “ValidationAttribute”, “IClientValidatable”.
The “ValidationAttribute“ class serves as base class for all validations and By overriding “Isvalid” method we can extend the validations.
The ValidateAttribute take two parameters value and the Validation context which holds all the control values.
For example I want to compare two dates.
Create a class with extends the validation attribute and create a property of compare to date field name. using validation Context, retrieve the value the compare to date field value and then
Compare with Self value .
public class GreaterDateAttribute : ValidationAttribute
{
public string EarlierDateField { get; set; }
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
DateTime? date = value != null ? (DateTime?)value : null;
var earlierDateValue = validationContext.ObjectType.GetProperty(EarlierDateField)
.GetValue(validationContext.ObjectInstance, null);
DateTime? earlierDate = earlierDateValue != null ? (DateTime?)earlierDateValue : null;
if (date.HasValue && earlierDate.HasValue && date < earlierDate)
{
return new ValidationResult(ErrorMessage);
}
return ValidationResult.Success;
}
}
