Difference between assembly n namespace
Namespace: It is a Collection of names wherein each name is Unique.
They form the logical boundary for a Group of classes.
Namespace must be specified in Project-Properties.
Assembly: It is an Output Unit. It is a unit of Deployment & a unit of versioning. Assemblies contain MSIL code.
Assemblies are Self-Describing. [e.g. metadata,manifest]
An assembly is the primary building block of a .NET Framework application. It is a collection of functionality that is built, versioned, and deployed as a single implementation unit (as one or more files). All managed types and resources are marked either as accessible only within their implementation unit, or by code outside that unit.
ADO.Net has some differences from ADO. The main differences are:
• ADO.Net is connectionless, rather than connection oriented. This means ALL datasets are disconnected. It does not mean you cannot keep a connection open, it just means that all the data you work with is a copy on the client side.
• ADO.Net can use XML
There are several important objects in ADO.Net we will briefly describe in the following table along with the most important properties or methods of those objects.
Objectt Purpose Important properties/methods
Connection To provide a connection to the data Properties:Connection String,data source, status,database
Methods: Open, Close, Dispose, ChangeDatabase, BeginTransaction,RollbackTransaction, CommittTransaction
The most important property of the connection object is the connection string. It provides the details of how to connect to a data source. Now here is an example of a connection string:
"Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=dbserver;Data Source=mydatabase;"
What are those different items and what do they mean? Well Data Source, if its SQL Server, is the name of the actual server (if its Access its the complete path to the database mdb file). Initial Catalog is the actual database on the server (if the database is Access, then there is no initial catalog). If you use the Sqlconnection you don't have a provider, but if you use the OleDBConnection the provider parameter tells it which driver to use. Most people figure those out pretty easily. However the 'Integrated Security=SSPI' confuses many people. Basically if you choose to use integrated security your options are: Integrated Security=SSPI This is for trusted domains with SQL Server or Access
Integrated Security=yes This is ony for use with Oracle
MSDN Connection String Entry
MSDN ADO.Net Entry
btw if you want to know more about what SSPI (Security Support Interface) is click HERE
Adapter Populates the dataset with data and resolves changes from the dataset back to the data source Methods: Fill, dispose, update<
Dataset can read databases or XML files. Similar to a recordset with CursorLocation = adUseClient, CursorType = asOpenStatus, LockType = adLockOptimistic
DataReader like an ado recordset with cursortype = adOpenForwardOnly and LockType = adLockReadOnly Properties: IsClosed,FieldCount
Methods: Close, GetBoolean, GetChars, GetByte, etc., Read, NextResult
Command Purpose Properties: CommandText,CommandTimeout default 30, CommandType (StoredProcedure, TableDirect, Text),Connection,Parameters
Methods: Cancel,CreateParameter,Dispose,ExecuteNonQuery,ExecuteReader,ExecuteScaler, ExecuteXML Reader
Data-releated namespaces
Namespace Purpose
System.Data This is the core ADO.net namespace
System.Data.Common Basic utility classes that are inherited by .Net providers
System.Data.SqlClient .Net SQL Server components
System.Data.Oledb .Net Generic components
System.Xml Classes and interfaces needed to support XML processing
Important Data Related Exceptions
• System.Data.DataException
• System.Data.RowNotInTableException
• System.Data.NoNullAllowedException
• System.Data.MissingPrimaryKeyException
• System.Data.InvalidExpressionException
• System.Data.SyntaxExpressionException
• System.Data.ConstraintException
• System.data.SQLClient.SQLClientException
• System.data.OleDBClient.OleDBClientException
Code Sample
Basic code to connect to an sql database ,fill textboxes, move forward and back, add, and save, is given here:
Public Class Form1
Inherits System.Windows.Forms.Form
Dim objcon As SqlConnection = New SqlConnection("Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=LPL_Rating;Data Source=dfwapp01;")
Dim myadapter As SqlDataAdapter = New SqlDataAdapter("Select top 100* From TblQuotes1", objcon)
Dim mydataset As New DataSet()
Dim currow As Integer
#Region " Windows Form Designer generated code "
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
objcon.Open()
myadapter.Fill(mydataset, "Select top 100* From TblQuotes1")
currow = 0
fill_textboxes(currow)
End Sub
Private Sub fill_textboxes(ByVal irow As Integer)
Try
TextBox1.Text() = mydataset.Tables(0).Rows(irow).ItemArray.GetValue(0).ToString
TextBox2.Text() = mydataset.Tables(0).Rows(irow).ItemArray.GetValue(1).ToString
TextBox3.Text() = mydataset.Tables(0).Rows(irow).ItemArray.GetValue(2).ToString
Catch e As Exception
MsgBox(e.ToString)
End Try
End Sub
Private Sub Button1_Click_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnnext.Click
currow += 1 fill_textboxes(currow)
End Sub
Private Sub btnPrev_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnPrev.Click
currow -= 1
fill_textboxes(currow)
End Sub
Private Sub btnadd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnadd.Click
TextBox1.Text = " "
TextBox2.Text = " "
TextBox3.Text = " "
End Sub
Private Sub btnsave_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnsave.Click
Dim newrow As DataRow = mydataset.Tables(0).NewRow
Dim icount As Integer
newrow(0) = TextBox1.Text
newrow(1) = TextBox2.Text
newrow(2) = TextBox3.Text
mydataset.Tables(0).Rows.Add(newrow)
myadapter.Update(mydataset, "tblquotes1")
End Sub
Adapter acts as a bridge between your data source and the dataset/datatable. The main advantage is it has all the data manipulation commands(select,insert,update,delete) and is highly sophisticated. but not needed all the time for us. Note, if you configure the adapter well in advance during design time, visual studio creates a connection also.
On the otherhands, a command object can be created runtime for a sql statement and works for an existing connection.
Adapter may be thought of an agent who could get/update data for us. It works in sync. with other data objects like dataset, datatable.
Command object is specifically designed for issuing a sql statement (including stored proc).
Classes and objects are separate but related concepts. Every object belongs to a class and every class contains one or more related objects.
Ø A Class is static. All of the attributes of a class are fixed before, during, and after the execution of a program. The attributes of a class don't change.
Ø The class to which an object belongs is also (usually) static. If a particular object belongs to a certain class at the time that it is created then it almost certainly will still belong to that class right up until the time that it is destroyed.
Ø An Object on the other hand has a limited lifespan. Objects are created and eventually destroyed. Also during that lifetime, the attributes of the object may undergo significant change.
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| Author: Sebastian 13 Jun 2008 | Member Level: Gold Points : 1 |
This is very informative. Thanks for sharing the details.
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