Create function with optional parameters

Question

4.00/5 (2 votes)

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Hi All,

I want to create a function as below VB Code with optional parameters

VB

Sub FIND_BTN(frm As Form, strTable As String, strCode As String, strDesc As String, ctlCode As String, Optional ctlDesc As Variant, _
    Optional vConn As Variant, Optional vFilter As Variant, Optional vDb As Variant, Optional Title As Variant, Optional ctlTo As Variant, _
    Optional ctlToDesc As Variant, Optional idx As Integer = -1, Optional fpsCtrl, Optional CodeCol As Long, Optional DescCol As Long)

Please help.

Posted 7-May-11 7:25am

Eager2Lern

Updated 7-May-11 8:38am

Kim Togo

v2

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3 solutions

Solution 2

Since .Net Framework 4.0 released, C# supports optional parameter.For detail just look Kim Togo link.

Posted 7-May-11 8:20am

Wonde Tadesse

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Kim Togo · Accepted Answer · 2011-05-07T07:44:00

Solution 1

As from .NET 4 you can make
Named and Optional Arguments[^]in method. Try read this link. Perhaps it can help you?

Posted 7-May-11 7:44am

Kim Togo

Comments

Tarun.K.S 7-May-11 13:46pm

Definitely should! 5+

Kim Togo 7-May-11 14:03pm

Thanks Tarun. If I remember correct. VB.NET had optional parameter long before C# ?

NuttingCDEF 7-May-11 14:27pm

That's my recollection too.

NuttingCDEF 7-May-11 14:27pm

Good answer - my 5.

Kim Togo 7-May-11 14:39pm

Thanks

Sandeep Mewara 7-May-11 14:45pm

Good link... 5!

Kim Togo 7-May-11 15:07pm

Thanks S Mewara.
I have tried to look at the method itself and the parameters as there are from VB.NET. But I do not understand VB.NET syntax good enough to translate the method into C# syntax.

Example, what type is "Optional fpsCtrl" => Is it a "object fpsCtrl = null".
And "Optional ctlToDesc As Variant" => Is it a "object ctlToDesc = null" ?

Sandeep Mewara 7-May-11 15:44pm

No Optional is not object.

Optional keyword is to define a variable as not required but passable in the method parameter.

Kim Togo 9-May-11 3:01am

Okay i understand "Optional" keyword. But what type is "fpsCtrl" ?

Sandeep Mewara 9-May-11 3:03am

Just a variable name, nothing else. You can write that as abcd to too! :)

Kim Togo 9-May-11 3:07am

Weird. Do not think that VB.NET is something for me :-)

Sergey Alexandrovich Kryukov 8-May-11 1:39am

Correct, my 5.
But... what to do if a .NET version prior to v.4 is required or v.4 is not available?

Please see the example in my solution.
--SA

Kim Togo 9-May-11 3:01am

Thanks SA.

Prasanta_Prince 8-May-11 2:28am

Good one 5 from me.

Kim Togo 9-May-11 3:00am

Thanks Prasanta

Sergey Alexandrovich Kryukov · Accepted Answer · 2011-05-07T19:37:00

Solution 3

In addition to the answer by Kim:

Before v.4.0, the only way of getting the effect of optional parameters with default was method overloading.
Here is how:

C#

const int DefaultB = 13;

//...

void MethodWithOptionalArguments(int a, int b, string c) { /*...*/ } // full parameter list

void MethodWithOptionalArguments(int a, int b ) { // shortened list
   MethodWithOptionalArguments(a, b, string.Empty);
}
void MethodWithOptionalArguments(int a) { // even shorter
   MethodWithOptionalArguments(a, DefaultB, string.Empty);
}

—SA

Posted 7-May-11 19:37pm

Sergey Alexandrovich Kryukov

Updated 26-May-11 9:55am

v2

Comments

Kim Togo 9-May-11 3:05am

My 5. Yes you are right SA. And if there many parameters that you what to have default values in. Then you have to make many overloads of one method. I come from a C++ world and moved to C#. And optional parameters was one that I really misses.

Sergey Alexandrovich Kryukov 9-May-11 3:31am

And this is the major reason for me to welcome v.4...
--SA