If statement problem

This should be easy but, I have a shipping system, where the user picks a shipment method, and a shipment weight must be based off the shipment method chosen. i.e If the user chooses 'Standard Air', which is on a drop down list in a combo box, the consignment weight must be =>1 and <1000.

I have made a variable, dConsignWeight as Double, and converted the textbox to a double with Cdbl(txtConsignWeight.Text).

Then I try to create the If statement.

If cmbShipmentMethod.Text = "Standard Air" Then
dConsignWeight >=1

This is where I get an error? What am I doing wrong? thanks.

The error?

If I try dConsignWeight >= 1 it says expression not a method

Yes just saw it.
Then
dConsignWeight >=1 you are trying to assign >=1 to dConsignWeight. :)

so how do I code it that dConsignWeight must be >=1 o.o

You cannot assign a value that you don't know exactly what value it is.
A value has a value it cannot be >= or <= .
You can evaluate the value only.P.E. saying
If cmbShipmentMethod.Text = "Standard Air" and dConsignWeight >=1
but you cannot assign dConsignWeight >=1.

I am assuming you have different rates based on weights,

>=1 and <1000 is a certain amount ?
>=1000 and <2000 is a certain amount ? etc....

If the way I have explained it is true, then assign the amount to the range

if dConsignWeight >=1 and <1000 then
amount = 50.00

then refer to amount

if dConsignWeight >=1 and dConsignWeight <1000

Just to be more clear.. you have to place if inside an if (in short.. nested if..)

Code:

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If cmbShipmentMethod.Text = "Standard Air" Then
if dConsignWeight >=1 and dConsignWeight <1000
  '-- do bla bla...
end if
end if

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Actually it's better to have the "and's" instead of another if.
That way you will not have to also parse the second if.
In this example it is ok but if you had many conditions to check then i wouldn't recommend nested if's.It will slow your program down.

Quote:

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Originally Posted by sapator

Actually it's better to have the "and's" instead of another if.
That way you will not have to also parse the second if.
In this example it is ok but if you had many conditions to check then i wouldn't recommend nested if's.It will slow your program down.

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What you say is just the opposite of what actually is.

Nested IFs won't slow down your program. However a single IF with many conditions with AND operator would definitely slow down the program. This is because nexted IFs don't cause all conditions to be evaluated while a single IF with many conditions joined with AND operator must evaluate all conditions irrespective.

Nested IFs make the code lines longer. But some people find it easier to read and maintain that way. So I won't comment on that aspect, as it is a matter of personal preference.

If you want to use a single IF with multiple conditions, consider using the new ANDALSO / ORELSE operators to join the conditions. They cause short-circuiting between the conditions and act same as nested IFs.