Shortcut sc=Shortcut.CtrlShiftM;
			
Keys     ks=(Keys)sc;
string   shc=string.Empty;
if((ks & Keys.Alt)!=0)     shc+="Alt+" ;   // или Keys.Alt.ToString()+"+"; 
if((ks & Keys.Control)!=0) shc+="Ctrl+";   // ??? Keys.Control.ToString() не стандарт для меню 
if((ks & Keys.Shift)!=0)   shc+="Shift+";  // или Keys.Shift.ToString()+"+"; 
shc+=((Keys)(ks & Keys.KeyCode)).ToString();

[DllImport("user32.dll", CharSet=CharSet.Auto)]		
public static extern int GetMenuString(int hMenu, int wIDItem, StringBuilder lpString, int nMaxCount, uint wFlag);
public const uint MF_BYPOSITION = 0x400;

int           rc;
string        ac=string.Empty, bs;
StringBuilder sb=new StringBuilder(100);

if(GetMenuString(this.contextMenu1.Handle.ToInt32(), 0, sb, sb.Capacity, MF_BYPOSITION)>0)
{ bs=sb.ToString();
  ac=((rc=bs.LastIndexOf("\t"))<0 || (rc+1)>=bs.Length) ? "" : bs.Substring(rc+1);
}