AddHandler Visual Basic Example

VB.NET > Statements > AddHandler

AddHandler link an event with an event handler at run time.

Example:

1. Add event to an object

Public Class Form1

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Dim Obj As New Class1
        ' Associate an event handler with an event
        AddHandler Obj.myEvent, AddressOf EvHandler
        Obj.Class1Event()
    End Sub

    Sub EvHandler()

        ' Handle the event
        MsgBox("EvHandler")
    End Sub

    Public Class Class1
        Public Event myEvent()
        Public Sub Class1Event()
            RaiseEvent myEvent()
        End Sub
    End Class

End Class

2. Handle events for dynamic runtime control

Enum type c# example

C# > Types > enum

Enum is s type that contains of a set of named constants called the enumerator list.
By default the first enumerator has the value 0, and the value of each successive enumerator is increased by 1.

• EnumMemberAttribute

Example:

A.

enum SomeMonths { January, February, March };
enum OtherMonths { April = 1, May }; //Enumerators can use initializers to override the default values

int v = (int)SomeMonths.January; // 0
v = (int)OtherMonths.May; // 2

B. String Enum

Long type C# Example

C# > Types > long

The long keyword is an integral type.
Range: –9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
Size: Signed 64-bit integer

Example:

long l = 21321321321;

long l1 = 21321321321L; // using suffix L

int i = 100L; // Error: Error 1 Cannot implicitly convert type 'long' to 'int'. An explicit conversion exists (are you missing a cast?)

int x = (int)100L; // OK

Serialization C#

C#  > Serialization  

Serialization  role is to save the state of an object. It converts an object into a stream of bytes. The reverse process is called deserialization.

• DataContractAttribute

DataContractAttribute C# example

C# > Serialization > DataContractAttribute

DataContract Attribute specifies that the type defines or implements a data contract and is serializable by a serializer.
EnumMember Attribute specifies that the field is an enumeration member and should be serialized.

Example:

namespace WindowsFormsApplication

{
    public partial class Form1 : Form
    {
        [DataContract]
        public enum Country
        {
            [EnumMember(Value = "USA")]
            USA,
            [EnumMember(Value = "DE")]
            Germany,
            [EnumMember(Value = "FR")]
            France,
            NotASerializableEnumeration
        }

        [DataContract (Name = "Customer")]

        public class Customer : IExtensibleDataObject
        {
            public Customer(string name,  Country cnt)
            {
                Name = name;
                Country = cnt;
            }
            private ExtensionDataObject extensionDataValue;
            public ExtensionDataObject ExtensionData
            {
                get { return extensionDataValue; }
                set { extensionDataValue = value; }
            }
            [DataMember]
            internal string Name;
            [DataMember]
            internal Country Country;
        }
        public Form1()
        {
            InitializeComponent();
        }
        private void Form1_Load(object sender, EventArgs e)
        {
            Customer p = new Customer("Microsoft", Country.USA );
            FileStream fs = new FileStream(@"C:\1.xml", FileMode.Create);
            try
            {
                DataContractSerializer ser = new DataContractSerializer(typeof(Customer));
                ser.WriteObject(fs, p);
            }
            catch (SerializationException exc)
            {
                 MessageBox.Show(exc.Message.ToString());   
            }
            finally
            {
                fs.Close();
            }
        }
     }
}

Search for files in directories and subdirectories C#

C# > Files > Search

GetDirectories: gets the names of subdirectories in a specified directory.
GetFiles: returns the names of files in a specified directory.

Example: Search for files in directories and subdirectories

          List<string> sfiles = new List<string>();
         FileDirSearch(@"C:\\", sfiles, "*.xml");

      void FileDirSearch(string sDir, List<string> sfiles, string pattern)

        {
            try
            {
                foreach (string d in Directory.GetDirectories(sDir))
                {
                    foreach (string f in Directory.GetFiles(d, pattern))
                    {
                        sfiles.Add(f);
                    }
                    FileDirSearch(d, sfiles, pattern);
                }
            }
            catch (Exception exc)
            {
                MessageBox.Show (exc.Message);
            }
        }

Control of Flow Keywords SQL Server

SQL Server > Control of Flow

Control of Flow keywords in SQL Server:

• WHILE

PrintPreviewDialog C# Example

C# > Print  > PrintPreviewDialog

PrintPreviewDialog is a dialog box form for printing from a Windows Forms application.






Example

In this example we will create a print document and print using PrintPreviewDialog. We will print some text on Print Page event

using System;

using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Drawing.Printing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication3

{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private void btnPrint_Click(object sender, EventArgs e)
        {
            PrintDocument document = new System.Drawing.Printing.PrintDocument();
            PrintPreviewDialog ppd = new PrintPreviewDialog();
            ppd.ClientSize = new System.Drawing.Size(500, 400);
            ppd.Location = new System.Drawing.Point(0, 0);
            document.PrintPage += new PrintPageEventHandler(Doc_PrintPage);
            ppd.Document  = document;
            ppd.ShowDialog();
        }
        private void Doc_PrintPage(object sender, System.Drawing.Printing.PrintPageEventArgs e)
        {
            string text = "Header";
            Font printFont = new  Font("Tahoma", 40, System.Drawing.FontStyle.Bold );
            e.Graphics.DrawString(text, printFont, Brushes.Blue, 0, 0);
            text = "Text";
            printFont = new Font("Tahoma", 30, System.Drawing.FontStyle.Regular);
            e.Graphics.DrawString(text, printFont, Brushes.Black , 0, 100);
        }
    }
}

Add operator SQL Server Example

SQL Server > Operators > Add

+ Operator adds two numbers.





Example

1. Add values from 2 numeric columns

create table #test(value int, fee int)
insert into #test(value, fee) values (500,50),(100,10)
  select
   value + fee as 'Total'
  from
   #test
drop table #test

Result:
 Total
   550
   110

2. Add values from 1 numeric value and 1 char value

DECLARE @int_value int = 100
DECLARE @str_value varchar(10) = '10'

SELECT @str_value + @int_value

Result:
(No column name)
110

3. Using + operator to concatenate string

DECLARE @str1 varchar(10) = 'Microsoft'
DECLARE @str2 varchar(10) = 'SQL Server'

SELECT @str1 + ' ' + @str2

Result:
(No column name)
Microsoft SQL Server

Rank DataTable with LINQ C# Example

C# > LINQ > Rank

Example: Using LINQ to implement RANK function with DataTable.

using System;

using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication3

{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        public  DataTable RankDt(DataTable dt, string fld)
        {
            var rankDt = (from row in dt.AsEnumerable()
                            orderby row.Field<int>(fld) descending
                            select row).CopyToDataTable();

            rankDt.Columns.Add("Rank");

            int rank = 1;
            for (int i = 0; i < rankDt.Rows.Count - 1; i++)
            {
                rankDt.Rows[i]["Rank"] = rank;
                if (rankDt.Rows[i][fld].ToString() != rankDt.Rows[i + 1][fld].ToString())
                    rank++;
            }
            rankDt.Rows[rankDt.Rows.Count - 1]["Rank"] = rank;
            return rankDt;
        }

        private void Form1_Load(object sender, EventArgs e)

        {
            DataSet ds = new DataSet();
            ds.Tables.Add("Product");
            DataTable dt = ds.Tables[0];
            dt.Columns.Add("name", typeof(string));
            dt.Columns.Add("quantity", typeof(Int32));
 
            DataRow dr = dt.NewRow();
            dr[0] = "Product 1" ;
            dr[1] = 500;
            dt.Rows.Add(dr);
            dr = dt.NewRow();

            dr[0] = "Product 2";

            dr[1] = 500;
            dt.Rows.Add(dr);

            dr = dt.NewRow();

            dr[0] = "Product 3";
            dr[1] = 50;
            dt.Rows.Add(dr);

            dr = dt.NewRow();

            dr[0] = "Product 4";
            dr[1] = 100;
            dt.Rows.Add(dr);

            dataGridView1.DataSource = RankDt(dt, "quantity");

        }
     }
}