private string say()
    {
        string method = @"namespace Yb
{
    public class helloworld
    {
        public helloworld()
        {
          
        }
        public string sayHello1(string str)
        {
            return str;
        }
        public string sayHello(string str,string str1)
        {
            return str+str1;
        }
    }
}";
        CodeSnippetCompileUnit unit = new CodeSnippetCompileUnit(method);
        CSharpCodeProvider provider = new CSharpCodeProvider();
        CompilerParameters paras = new CompilerParameters();

        paras.ReferencedAssemblies.Add(" System.dll");
        paras.ReferencedAssemblies.Add(" System.Data.dll");
        paras.ReferencedAssemblies.Add(" System.Data.SqlClient.dll");
        paras.GenerateInMemory = true;
        paras.GenerateExecutable = false;
        Assembly asm = provider.CompileAssemblyFromDom(paras, unit).CompiledAssembly;
        Type type = asm.GetType("Yb.helloworld");
        MethodInfo mi = type.GetMethod( "sayHello1" , BindingFlags.Public | BindingFlags.Instance);
        object obj = asm.CreateInstance("Yb.helloworld");
        string returnstr = mi.Invoke(obj, new object[] { "helloworld" }).ToString();

        return returnstr;

    }