Resize Mulit-dimensional array

Question

Is this possible?
public string[,] MyArray = new string[99,999];
the above works but is either too large or not big enough.
public string[,] MainKeys = new string[,]; 
generates error "Array creation must have array size or array initializer"

Array.Resize(ref MyArray,100,1000);
generates error "'System.Array' does not contain a definition for 'Resize'".