Check if a BSTR is empty

I have a variant that contains a BSTR, but sometimes the BSTR is "" (empty), so how开发者_运维技巧 to avoid this? I have tried something like:

variant.bstrVal != NULL

But it didn't work.

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Use SysStringLen:

if (SysStringLen(variant.bstrVal) == 0)
{ ... }

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You can test the vt member of VARIANT for VT_NULL or VT_EMPTY

if (variant.vt != VT_NULL)
{
   ...
}