Why not use a specially designed class BitArray?
http://msdn.microsoft.com/query/dev11.query?appId=Dev11IDEF1&l=EN-US&k=k(System.Collections.BitArray);k(TargetFrameworkMoniker-.NETFramework,Version%3Dv4.5);k(DevLang-csharp)&rd=true
e.g.
BitArray array = new BitArray(150); // <- up to 150 bits
...
array[140] = true; // <- set 140th bit
array[130] = false; // <- reset 130th bit
...
if (array[120]) { // <- if 120th bit is set
...