one or more types required to compile a dynamic expression c# -

i have looked at: one or more types required compile dynamic expression cannot found. missing references microsoft.csharp.dll , system.core.dll? after trying top solution other solutions i've researched still unable resolve error. vs targeting .net 4.5.1. in addition, reference csharp added well. why still getting error?

using system; using system.collections.generic; using system.linq; using system.text; using system.runtime.interopservices; using system.net; using important.coreinterfaces; using adaptive.simplebinaryencoding;  private static t method<t>(byte[] pinned_memory, ref int offset)             {                 //dynamic var = typeof(t);                 dynamic temp = 1;                 directbuffer tempd = new directbuffer(pinned_memory);                 char messagetype = (char)pinned_memory[offset];                 switch(messagetype)                 {                     case 'h':                         dostuff();                         break;                     case 'd':                         dootherstuff();                         break;                     case 'a':                         stuff();                         break;                     case 'm':                         break;                     case 'p':                         break;                     case 'f':                         break;                     case 'k':                         break;                     case 'o':                         break;                     case 'c':                         break;                     case 'x':                         break;                     default:                         break;                 }                  messageheaderencoder header = new messageheaderencoder();                 header.wrap(tempd, offset, 1);                 temp.wrapfordecode(tempd, offset, temp.sbeblocklength(), temp.sbeschemaversion());              }