前端的資料卻無法傳遞至API

可是你給的資訊沒有前端

你確定這兩個是在同一個站裡面嗎?
你確定你的路徑正確嗎?

這是一段處理客戶登入的API(一樣是傳入帳號密碼)，提供給你參考

//回傳Format(json type)
{
	"status": {
		"code": 0,
		"message": "success"
	},
	"data": {
		"result": "xxx"
	}
}

//[Controllers]
[HttpPost]
public object custlogin([FromBody]request_login req)
{
    SqlConnection conn = new SqlConnection(connstr_db);
    conn.Open();

    signup_root root = new signup_root();
    response_status status = new response_status();
    signup_data data = new signup_data();

    if (req.name.Length>0 && req.pwd.Length>0)
    {
        string sql = "";
        SqlCommand sqlcmd;

        sql = "select * from users ";
        sql += "where name='" + req.name + "' and pwd='" + req.pwd + "'";
        sqlcmd = new SqlCommand(sql, conn);
        SqlDataReader dr = sqlcmd.ExecuteReader();

        if (dr.HasRows)
        {
            while (dr.Read())
            {               
                status.code = "0";
                status.message = "success";   
                
                data.result=req.name+"/"+req.pwd;
                
                root.status = status;
                root.data = data;
            }
        }
        else
        {
            status.code = "-1";
            status.message = "Not Found.";
            
            data.result="NULL";

            root.status = status;
            root.data = null;
        }
        dr.Close();
        dr.Dispose();
        sqlcmd.Dispose();
    }
    else
    {
        status.code = "-2";
        status.message = "Input Error!!";
        
        data.result="NULL";

        root.status = status;
        root.data = null;
    }
    conn.Close();
    conn.Dispose(); 

    return root;
}

//[Models]
//接收傳入的帳密
public class request_login
{
    public string name { get; set; }
    public string pwd { get; set; }
}

//回傳格式    
public class signup_root
{
    public response_status status { get; set; }
    public signup_data data { get; set; }
}
    
public class response_status
{
    public string code { get; set; }
    public string message { get; set; }
}
    
public class signup_data
{
    public string result { get; set; }
}