我也是，怎么解決

在Teacher.cpp文件里面提示Teacher是未聲明的類或命名空間名

//Teacher.h文件
#include?<string>
using?namespace?std;
class?Teacher
{
public:
	void?setName(string?_name);
	string?getName();
	void?setGender(string?_gender);
	string?getGender();
	void?setAge(int?_age);
	int?getAge();
	void?study();
private:
	string?m_strName;
	string?m_strGender;
	int?m_iAge;
};

//Teacher.cpp文件
#include?"Teacher.h"
#include<iostream>
#include?"stdafx.h"

using?namespace?std;
void?Teacher::setName(string??_name)
{
	m_strName?=?_name;
}
string?Teacher::getName()
{
	return?m_strName;
}
void?Teacher::setGender(string?_gender)
{
	m_strGender?=?_gender;
}
string?Teacher::getGender()
{
	return?m_strGender;
}
void?Teacher::setAge(int?_age)
{
	m_iAge?=?_age;
}
int?Teacher::getAge()
{
	return?m_iAge;
}
void?Teacher::study()
{
	cout?<<?"?let`s?study..."?<<?endl;
}


//demo.cpp
#include?"stdafx.h"
#include"Teacher.h"
#include?<iostream>
#include<String>

using?namespace?std;

int?main()
{
	Teacher?A;
	A.setName("Alex");
	A.setGender("male");
	A.setAge(19);
	cout?<<?A.getName()?<<?""?<<?A.getGender()?<<?""?<<?A.getAge()?<<?endl;
	A.study();
	return?0;
}