为啥运行的结果总是1。求解！！！

#include<stdio.h>
#define ENDSTRING '\0'
extern int StrLen(char* str);
int main (void)
{
    char src[]="Hello Dymatic ";
    printf("string length is : %d\n",StrLen(src));
    return 0;
}
   
int StrLen( char *string)
{
    int len = 0;
    while(*string++ != 'ENDSTRING);
    len++;
    return len;
}