link sql with c#

Ado.net Provides various Class which can be used for datasource Communication under the following namespaces:

System.Data

System.Data.SqlClient
System.Data.OleDb
System.Data.Odbc

System.Data: collections of type  use to holding and managing data on client machine.

System.Data.OleDb: collections of type  use to communicate with any Datasource.

System.Data.SqlClient: collections of type  use to Communicate only with SqlServer

System.Data.Odbc: collections of type  use to communicate with traditional odbc drivers.

above namspaces contain set of class as following

Connection,Command,DataReader,DataAdapter,CommandBuilder etc.

Note :Each Class Reffered By Prefexing With Namwspace Name Like:

oledbConnection,SqlConnection etc

this is the Sample Example in this example we r fetching Data from Database and showing into Combobox.

Design Form Take one Combobox with name cmbcolumn write following code.

Imports System.Data.SqlClient;
Public Class Form1
    Dim cn As SqlConnection
    Dim cmd As SqlCommand

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Try
            cn=New SqlConnection("Server=[Servername where ur databse store];database=[Databasename];uid=sa;pwd=[password]");
            cmd = New SqlCommand()
            cmd.Connection = cn
            cmd.CommandText = "Select [columnname] from [Tablename]"
            cn.Open()
            'perform any operation which u want with data like
            Dim dr As SqlDataReader = cmd.ExecuteReader()
            While dr.Read()
                cmbcolumn.Items.Add(dr(0)) 'here cmbcolumn is a comboBox 
            End While

            cn.Close()

        Catch ex As Exception
            MessageBox.Show(ex.Message)

        End Try
    End Sub
End Class

If this information is useful for u plz mark as accepted answer