Check for multiple file attributes

[Pete Kane]

Hello all, how can I check for multiple file attributes using bitwise
operators ? I'm thinking along the lines of


string fname = "c:\\test.txt";
if(File.GetAttributes(fname) & (FileAttributes.ReadOnly |
FileAttributes.Archive ))

{

File.SetAttributes(fname,FileAttributes.Normal);

}

Basically I'm trying to say "If Readonly or Archive" then set the attribute
to normal, as you can tell I'm new to C#

 

[Nicholas Paldino [.NET/C# MVP]]

Pete,

Yes, the FileAttributes enumeration is a bitwise mask, so you would
compare in that manner. However, you do have to make sure the result is not
zero, because C# does not assume that a non zero integer value evaluates to
true, rather, you have to use a boolean value.

In essence, you need to change your expression to this:

if ((File.GetAttributes(fname) & (FileAttributes.ReadOnly |
FileAttributes.Archive)) != 0)

Hope this helps.

 

[Pete Kane]

sorry Nicholas I posted directly to you, I thought I was on the right lines
but it's nice to have confirmation, BTW what's the difference between | and
|| ?

regards

Pete Kane

Pete,

Yes, the FileAttributes enumeration is a bitwise mask, so you would
compare in that manner. However, you do have to make sure the result is
not zero, because C# does not assume that a non zero integer value
evaluates to true, rather, you have to use a boolean value.

In essence, you need to change your expression to this:

if ((File.GetAttributes(fname) & (FileAttributes.ReadOnly |
FileAttributes.Archive)) != 0)

Hope this helps.


--
- Nicholas Paldino [.NET/C# MVP]
- (e-mail address removed)

Hello all, how can I check for multiple file attributes using bitwise
operators ? I'm thinking along the lines of


string fname = "c:\\test.txt";
if(File.GetAttributes(fname) & (FileAttributes.ReadOnly |
FileAttributes.Archive ))

{

File.SetAttributes(fname,FileAttributes.Normal);

}

Basically I'm trying to say "If Readonly or Archive" then set the
attribute to normal, as you can tell I'm new to C#

 

[Nicholas Paldino [.NET/C# MVP]]

Pete,

|| (and &&) are logical operators, meant to be used on boolean types. |
(and &) are bitwise operators, meant to be used on integral types for bit
masking.


--
- Nicholas Paldino [.NET/C# MVP]
- (e-mail address removed)

sorry Nicholas I posted directly to you, I thought I was on the right
lines but it's nice to have confirmation, BTW what's the difference
between | and || ?

regards

Pete Kane

Pete,

Yes, the FileAttributes enumeration is a bitwise mask, so you would
compare in that manner. However, you do have to make sure the result is
not zero, because C# does not assume that a non zero integer value
evaluates to true, rather, you have to use a boolean value.

In essence, you need to change your expression to this:

if ((File.GetAttributes(fname) & (FileAttributes.ReadOnly |
FileAttributes.Archive)) != 0)

Hope this helps.


--
- Nicholas Paldino [.NET/C# MVP]
- (e-mail address removed)

Hello all, how can I check for multiple file attributes using bitwise
operators ? I'm thinking along the lines of


string fname = "c:\\test.txt";
if(File.GetAttributes(fname) & (FileAttributes.ReadOnly |
FileAttributes.Archive ))

{

File.SetAttributes(fname,FileAttributes.Normal);

}

Basically I'm trying to say "If Readonly or Archive" then set the
attribute to normal, as you can tell I'm new to C#

 

[Pete Kane]

thanks Nicholas, have a good Xmas...

regards

Pete Kane

Pete,

|| (and &&) are logical operators, meant to be used on boolean types.
| (and &) are bitwise operators, meant to be used on integral types for
bit masking.


--
- Nicholas Paldino [.NET/C# MVP]
- (e-mail address removed)

sorry Nicholas I posted directly to you, I thought I was on the right
lines but it's nice to have confirmation, BTW what's the difference
between | and || ?

regards

Pete Kane

Pete,

Yes, the FileAttributes enumeration is a bitwise mask, so you would
compare in that manner. However, you do have to make sure the result is
not zero, because C# does not assume that a non zero integer value
evaluates to true, rather, you have to use a boolean value.

In essence, you need to change your expression to this:

if ((File.GetAttributes(fname) & (FileAttributes.ReadOnly |
FileAttributes.Archive)) != 0)

Hope this helps.


--
- Nicholas Paldino [.NET/C# MVP]
- (e-mail address removed)


Hello all, how can I check for multiple file attributes using bitwise
operators ? I'm thinking along the lines of


string fname = "c:\\test.txt";
if(File.GetAttributes(fname) & (FileAttributes.ReadOnly |
FileAttributes.Archive ))

{

File.SetAttributes(fname,FileAttributes.Normal);

}

Basically I'm trying to say "If Readonly or Archive" then set the
attribute to normal, as you can tell I'm new to C#