Is SPWeb AllowUnsafeUpdates is an expensive process?

Question

Is SPWeb AllowUnsafeUpdates is an expensive process ?

I want to do it 3-4 times, is it heavy process ?

Answer 1

It might look like a property, but actually the setter of that property calls a method named SetAllowUnsafeUpdates(value) which has the following code:

private void SetAllowUnsafeUpdates(bool allowUnsafeUpdates)
{
   this.Request.SetIgnoreCanary(allowUnsafeUpdates);
}

SetIgnoreCanary sets to ignore Canary (Canary is something that refers to a method of buffer overflow protection (https://en.wikipedia.org/wiki/Buffer_overflow_protection#Canaries)) and checks if permissions are properly propagated:

public void SetIgnoreCanary(bool bIgnoreCanary)
{
   try
   {
      ++this.m_UnmanagedStackCount;
      this.EnsureRightsPropagated();
      this.m_SPRequest.SetIgnoreCanary(bIgnoreCanary);
   }

    [....] SOME CODE OMITTED
 }

by calling EnsureRightsPropagated:

private void EnsureRightsPropagated()
{
  if (this.m_pa.Permissions == this.m_permsAdded)
    return;
  this.m_SPRequest.GrantAdditionalPermissions((ulong) this.m_pa.Permissions);
  this.m_permsAdded = this.m_pa.Permissions;
}

And the latter "assigns" additional permissions for the current SPRequest by calling GrantAdditionalPermissions:

public void GrantAdditionalPermissions(ulong mask)
{

}

Which apparently is an empty method :)

So, I assume it's not very resource expensive.

Answer 2

it is no process at all, it is just a flag. But you should avoid it due to security reasons. If you place the Digest-Control from SharePoint on your page or do a SPUtility.ValidateDigest() by yourself in code, you should be able to update without AllowUnsafeUpdates