C/C++ :: Return File Contents As String

I am trying to code a function which will read a file on system and return its content back as string. Code is below.

char * readtxt(){
    FILE * fptr;
    char  c;
    static char txt[30];
    int len=0;  
    fptr = fopen("C:UsersTestDesktopDev est.txt", "r");  

[Code] ....

I suppose txt variable is pointer. But I need to return the file content as string so the function structure should look like

returnType function(){
return "File Contents as String";
}

How can I achieve this ?