Visual Basic.NET

1. Visual Basic.NET • Declaring Variables • Dim x As Integer • Dim y As Integer = 10 • Comments • ' comment • Assignment Statement • var= newvalue • Constant • Const Pi As Double = 3.14159

2. Visual Basic.NET Data Types Visual Basic .NET Runtime Storage Range of Values Data Type Data Type Size ============================================================ Boolean System.Boolean 4 bytes True or False Byte System.Byte 1 byte 0 to 255 (unsigned) Char System.Char 2 bytes 1 Unicode “” character Date System.DateTime 8 bytes January 1, 0001to December 31,9999 Decimal System.Decimal 12 bytes +/-0.0 79,228,162,514,264,337, 593,543,950,335 Double System.Double 8 bytes -1.797693134862310.0E308 to - 4.94065645841247E-324 Integer System.Int32 4 bytes -2,147,483,648 to 2,147,483,647 Long System.Int64 8 bytes -9,223,372,036,854,775,80 to 9,223,372,036,854,775,807 Object System.Object 4 bytes Any data type Depends on usage. Short System.Int16 2 bytes -32,768 to 32,7670 Single System.Single 4 bytes -3.402823E38 to 0.0 String System.String 10 bytes 0 to approximately billion Unicode char

3. Data Types • Option Explicit: forces variable declaration • Option Strict: forces variable declaration + will not allow conversions where data loss would occur. • Data Type Conversion • CType (variable_name, New type) • ToString method is available in all data types • Members available for data types • String (Trim, Length, Substring, Replace,..) • Array (Length, GetUpperBound, Clear, Sort,..) • DateTime (Now,Today,Year,Day,Hour, Add, Subtract, IsLeapYear, DaysInMonth, …)

4. VB.NET Operators Type Operator Purpose Example Math + Add 5 + 2 = 7 – Subtract 5 – 2 = 3 * Multiply 5 * 2 = 10 / Divide 5 / 3 = 2.5 \ Integer Divide 5 \ 2 = 2 ^ Exponentiation 5^2 = 25 Mod Remainder 5 mod 2 =1 String + Concatenate “one” + “two” = “onetwo” & Concatenate “one” & “two” = “onetwo” Assignment = Assigns the value of expression to variable x = 5 + 3 Math += Adds the value x += y

5. Type Operator Purpose Example -= Subtracts the x -= y *= Multiplies the x *= y /= Divides the x /= y \= Integer divides x \= y &= Concatenates the x &= y ^= Exponentiates x ^= y Comparison = Is equal to If (x = y) < Is less than If (x < y) <= Is less than or If (x <=equal to y) > Is greater than If (x > y) >= Is greater than If (x >=or equal to y) <> Is not equal to If (x <> y) Like Matches a pattern If (x Like “p??r”) Is Do object variables refer to same object If (x Is y) Logical And True if both expressions are true If (x = 3 AND y=4) Or True if one or If (x = 3 OR y=4) both expressions are true Not True if expression is false If Not (x =5) Xor True if one expression is If (x = 3 Xor y=4) true, but not both

6. Arrays • Specify upper bound of array, starting at index 0 Dim Names(9) As String `10 elements 0 to 9 Dim Num () As Integer = { {1,6} , {7,5} , {5,9} } Names(0) = “Ahmed” Num (2,1)=4 ReDim Preserve Names(2) For Each e in Num print e `Read only elements Next

7. Enumeration Enum UserType Admin =3 Guest = 2 User= 9 End Enum Dim user As UserType = UserType.Guest Dim user2 As UserType = 9

8. Branching Structures If (condition) Then code Elseif (condition) then another code Else final code End if

9. Branching Structures Select Case expresssion Case 1 code 1 Case 2 code2 Case 3 code3 Case Else Default code End Select

10. Looping Do While (condition) code to repeat Loop ___________________ Do code to repeat Loop until (condition) • Exit Do `to get out of a loop

11. Looping For i = init_value To final_value Code to repeat Next • Exit for ` to get out of loop

12. Subroutines and Functions • Subroutines Sub HelloWorld() Response.Write(“Hello World”) End Sub You call a sub using either of the following statements: HelloWorld() Call HelloWorld() • Functions: can return a value to calling program Function SayHello() As String Return “Hello World” End Function • NOTE • VB.NET requires parentheses around argument lists • The default is to pass parameters by value otherwise use “byref” keyward • Overload functions of procedures using the “overloads” keywaord