why does this code throw a null reference exception in c# but ok in c++ EQSTATE es;//<-ok. not ok->es.lg = 1.0;

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I have converted a c++ project(which runs) to c# where it throws a null reference exception here is a small sample

public class EQSTATE
{...public double lg; // low  gain...
}
EQSTATE es;

init_3band_state(es, 880,5000,480000);
Then
private void init_3band_state(EQSTATE es, int lowfreq, int highfreq, int mixfreq)
{
  // Clear state
  //memset(es, 0, sizeof(EQSTATE)); does not compile in C++ nor of course c# but runs without it
  es.lg = 1.0; //=============this is where the null reference exception is thrown
  es.mg = 1.0; ditto
  es.hg = 1.0; ditto
}

Posted 13-Apr-15 18:56pm

Member 10987276

Updated 13-Apr-15 18:57pm

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Member 10987276 14-Apr-15 1:47am

Thanks for the quick reply. EQSTATE es = new EQSTATE(); this worked best as it required less mods to code.

Member 10987276 14-Apr-15 1:57am

And the struct fix worked without the 'new EQSTATE'

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Shmuel Zang · Accepted Answer · 2015-04-13T19:12:00

In C++ es defines a value on the stack. In C# es defines a reference that should be initialized with an actual object (using the new keyword).

For initializing es with an object (on the heap), you can change the definition to something like:

C#

EQSTATE es = new EQSTATE();

P.S. You can define es on the stack also in C#, by making EQSTATE a value type (by using the struct keyword instead of class).