C# object[] array getlength?

Hello what is the equivalent of getlenght on an object array it only seems to work with basic arrays like int,double,float,string etc.

 int[,] myInts = new int[20,20];
 
 myObect[,] ob = new myObject[20,20]
 
 for (int i = 0; i < myInts.getLength(1);i++) {
     //do some stuff
 }
 
 //dosent work whats the equivalent of get length?
 for (int z= 0; i < ob.getLength(1);z++) {
     //do some stuff
 }