myFile.IsReadOnly = false;

…or, as ripper234 wrote:

myFile.Attributes &= ~FileAttributes.ReadOnly;

Neither of these methods require a pre-test as they ALWAYS remove read-only status.

————–
Scott’s solution (using the -= assignment operator) is dangerous for two reasons:
(1) It works ONLY IF the ReadOnly attribute is set, thus a test is required beforehand.
(2) It is performing a subtract operation, which is not is not the best choice when working with binary flags. The subtract operation works if condition 1 (above) is true, but additional subtract operations will ALTER OTHER BITS in the FileAttributes field!

To appropriately manipulate binary flags, you should only use bitwise (binary) operators:

& (bitwise AND) – clears bits
| (bitwise OR) – sets bits
^ (bitwise XOR) – flip-flops bits
~ (bitwise negation) – flip-flops all bits

You can also use the corresponding compound assignment counterparts:

&= (bitwise AND and assign)
|= (bitwise OR and assign)
^= (bitwise XOR and assign)

Not appropriate for flags, but appropriate for other binary operations:

<> (shift right) – moves bits to the right (same as divide by n^2, but faster)

———–

How ripper234’s method works:

FileAttributes.ReadOnly = 0×0000000000000001

In order to use the bitwise AND operator to clear a bit, we need the complement of this:

~FileAttributes.ReadOnly = 0×1111111111111110

Next, we perform the bitwise AND, then assign it back:

myFile.Attributes = myFile.Attributes & ~FileAttributes.ReadOnly;

The &= operator is shorthand for the above and yields:

myFire.Attributes &= ~FileAttributes.ReadOnly;

This works:

FileInfo info = new FileInfo(file);
info.Attributes &= ~FileAttributes.ReadOnly;

Dim myFile As FileInfo = New FileInfo(“c:\myfile.txt”)

If myFile.IsReadOnly ThenThen
‘ remove the read only attribute
myFile.IsReadOnly = False
End If