c# - Are there other functions that can result in "StartIndex cannot be less than zero"? -

we have customer reported receiving error message along lines of "startindex cannot less zero. parameter name: startindex". standard error message thrown in substring , remove functions of string class. unfortunately, unable ahold of data failing on them, i'm forced debug looking @ source code.

i have looked incidences of substring , remove , verified startindex parameter not less 0. searched uses of "startindex" , verified that, in 2 cases being used first parameter of string function, not mathematically less 0 (in both cases, given return value of indexof function, string length , value of 2 added it, 1 smallest value have).

this suggests me either issue fixed in prior codebases, have nonstandard codebase, or i'm looking in wrong place. there other functions in c# raise sort of error text? or there way in reporting wrong input parameter? misunderstanding error message?

here's 91 methods system.dll , mscorlib.dll:

static class program {     static void main()     {         var names =             getmethodswithparameter(typeof(object), "startindex")             .concat(getmethodswithparameter(typeof(uri), "startindex"))         .distinct();         foreach(var name in names)         {             console.writeline(name);         }     }      private static ienumerable<string> getmethodswithparameter(type assemblyorigin, string name)     {         foreach(var type in assemblyorigin.assembly.gettypes())         {             foreach(var method in type.getmethods(                 bindingflags.public | bindingflags.nonpublic | bindingflags.instance | bindingflags.static))             {                 if(method.getparameters().any(x => x.name == name))                 {                     yield return type.fullname + "." + method.name;                 }             }         }     } }