How can I use the null value as the parameter?

[Jet]

Hi all,
I had a code like the follow:
class A{
...
public void get(int i,params OleDbParameter[] p)
{
if((p!=null)||( p.Length>0))
{
// Do some work
}
else
{
// Do another work
}

}
....
}
And in other class I had create the instance which include this method , and
I had not the OleDbParameter[] parameter tranfer to this method.And I try to
do it like this to call the method:
....
A _a=new A();
int i=100;
_a.get(i,(OleDb Parameter[])null);
....

But when it run to the method it throw me a "NullRefranceEx ception"
How can I solve this problem? Why I can't give it the null value as the
parameter tranfer to the get() method? I also declare the null value as the
type OleDbParameter[].

[Larry Lard]

Jet wrote:

Hi all,
I had a code like the follow:
class A{
...
public void get(int i,params OleDbParameter[] p)
{
if((p!=null)||( p.Length>0))
Do you actually mean

if((p!=null)&&( p.Length>0))

?

{
// Do some work
}

Everything else looks OK.

--
Larry Lard
Replies to group please

[Dave]

If a parameter is modifed with the "params" keyword, you can completely ignore the parameter, however, the framework guarantees that
the Array will be initialized and empty:

public void MyMethod(int i, params OleDbParameter[] p)
{
if (p.Length > 0)
{
// Todo: work
}
}

MyMethod( 100 ); // ignores the parameter array argument

--
Dave Sexton
dave@www..jwaon line..com
-----------------------------------------------------------------------
"Jet" <li******@126.c om> wrote in message news:%2******** ********@TK2MSF TNGP15.phx.gbl. ..

Hi all,
I had a code like the follow:
class A{
...
public void get(int i,params OleDbParameter[] p)
{
if((p!=null)||( p.Length>0))
{
// Do some work
}
else
{
// Do another work
}

}
...
}
And in other class I had create the instance which include this method , and I had not the OleDbParameter[] parameter tranfer to
this method.And I try to do it like this to call the method:
...
A _a=new A();
int i=100;
_a.get(i,(OleDb Parameter[])null);
...

But when it run to the method it throw me a "NullRefranceEx ception"
How can I solve this problem? Why I can't give it the null value as the parameter tranfer to the get() method? I also declare the
null value as the type OleDbParameter[].

[Jon Skeet [C# MVP]]

Dave <NO*********@do tcomdatasolutio ns.com> wrote:

If a parameter is modifed with the "params" keyword, you can
completely ignore the parameter, however, the framework guarantees
that the Array will be initialized and empty:

public void MyMethod(int i, params OleDbParameter[] p)
{
if (p.Length > 0)
{
// Todo: work
}
}

MyMethod( 100 ); // ignores the parameter array argument

No, it's not guaranteed to be non-null - the caller can specify a null
value as the OP actually had. I believe that Larry nailed the problem.

Here's an example of a params parameter being null:

using System;

class Test
{
static void Main()
{
SomeMethod((str ing[])null);
}

static void SomeMethod(para ms string[] names)
{
if (names==null)
{
Console.WriteLi ne ("I'm null!");
}
else
{
foreach (string name in names)
{
Console.WriteLi ne (name);
}
}
}
}

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Dave]

Yes, you are right.

I tried and it seems that just passing "null", without casting, works too.

So, it gaurantees that the value will be initialized empty unless the caller explicitly passes null.

Sound good?

--
Dave Sexton
dave@www..jwaon line..com
-----------------------------------------------------------------------
"Jon Skeet [C# MVP]" <sk***@pobox.co m> wrote in message news:MP******** *************** *@msnews.micros oft.com...

Dave <NO*********@do tcomdatasolutio ns.com> wrote:

If a parameter is modifed with the "params" keyword, you can
completely ignore the parameter, however, the framework guarantees
that the Array will be initialized and empty:

public void MyMethod(int i, params OleDbParameter[] p)
{
if (p.Length > 0)
{
// Todo: work
}
}

MyMethod( 100 ); // ignores the parameter array argument

No, it's not guaranteed to be non-null - the caller can specify a null
value as the OP actually had. I believe that Larry nailed the problem.

Here's an example of a params parameter being null:

using System;

class Test
{
static void Main()
{
SomeMethod((str ing[])null);
}

static void SomeMethod(para ms string[] names)
{
if (names==null)
{
Console.WriteLi ne ("I'm null!");
}
else
{
foreach (string name in names)
{
Console.WriteLi ne (name);
}
}
}
}

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Jon Skeet [C# MVP]]

Dave <NO*********@do tcomdatasolutio ns.com> wrote:

Yes, you are right.

I tried and it seems that just passing "null", without casting, works
too.
Right. I like to make it explicit, so it's clear I'm not trying to pass
a single string parameter.
So, it gaurantees that the value will be initialized empty unless the
caller explicitly passes null.

Sound good?

Yup.

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too