Conditional statements
- 3. Conditions are logical expressions that evaluate to a True/False value and they usually contain comparison operators— equals (=), different (<>), less than (<), greater than (>), less than or equal to (<=), and so on — and logical operators: And, Or, X or, and Not. Here are a few examples of valid conditions:
- 4. If (age1 < age2) And (age1 > 12) Then ... If score1 = score2 Then ...
- 5. FORMS OF IF STATEMENT 1. if … statement then 1 condition 2. if … statement has Else part 3. if statement has one or more Else if parts
- 6. If … then statement The If. . .Then statement tests an expression, which is known as a condition. If the condition is True, the program executes the statement(s) that follow. The If. . .Then statement can have a single-line or a multiple-line syntax. To execute one statement conditionally, use the single-line syntax as follows: If condition Then statement is TRUE End if
- 7. Code: Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click If TextBox1.Text = "Hello!" Then Label1.Text = "World" End Sub
- 8. Another example: Dim a As Integer Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click a = TextBox1.Text If a >= 18 Then label1.text ("You can now vote online.") End Sub
- 9. 2. if … statement has Else part If the condition is evaluates correct, then the statement are executed. If the condition is evaluates false, then the statements are executed. Syntax: If condition Then statement is True Else statement is False End if
- 10. Dim a As Integer Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click a = TextBox1.Text If a >= 18 Then Label1.Text = "You can now vote online." Else Label1.Text = "You can not vote“ End Sub
- 11. Another Example: (Using Boolean/Logical Operation) If TextBox1.Text = “Apple" And / Or TextBox2.Text = “Banana" Then Label1.Text = "Fruit“ Else Label1.Text = “Junk Food"
- 12. 3. if statement has one or more Elseif parts One or more statements and condition. Syntax: If Condition1 then statements to be if condition is true Else if condition2 then statements to be executed is False but Condition2 is True Else if condition3 then statements to be executed if Con1 and Con2 are False but Condition3 is True Else statements to be executed if all of the above conditions are False. End Sub
- 13. Dim Grade as Integer Grade = txtgrade.Text If Grade <= 74 Then MsgBox("You Failed!") Else If Grade <= 80 Then MsgBox("Needs Improvement!") Else If Grade <= 85 Then MsgBox("Average!") Else If Grade <= 90 Then MsgBox("Satisfactory!") Else If Grade <= 95 Then MsgBox("Very Satisfactory!") Else MsgBox("Excellent!") End Sub
- 14. Note: Aside from Message box, you may also use the controls such as label and textbox, if you want to show the executed statements or condition.