Hi Dharmesh,
MathWorks offers two different products which may accomplish this, depending on your requirements.
One option is to use MATLAB Coder to generate portable C or C++ code, which can then be compiled into a standalone DLL. There are several limitations with this workflow; an overview can be found on this page. Additionally, only some MATLAB functions support code generation, and some of those that do have limitations. You can review all functions which support code generation here.
Another option is to use MATLAB Compiler to generate a library file which can be used in a C# project. This workflow has fewer limitations (the pages I linked in the above paragraph do not apply), but the generated executable or library file will depend on the MATLAB Compiler SDK. Here's a good page to help you get started with MATLAB Compiler for C# projects.
Matthew