c# – 将类型字符串转换为类型对象

public static User FindUser(User[] users,int noteid)
{       
    foreach (User user in users)                
        if (user.ID == noteid) return user.FullName;
    return null;
}

期望在成功找到一个字符串对象时返回一个字符串对象(user.FullName值),而您为方法声明的返回类型是User.你应该做的就是这个(你当前正在调用FindUser的地方：

var ArrayOfUsersToSearch = GetAnArrayOfUserFromSomewhere();
var noteId = 3; // Or whatever value you want to use
var myUserToFind = FindUser(ArrayOfUsersToSearch,noteId);

Console.WriteLine("The users full name is: {0}",myUserToFind != null ? myUserToFind.FullName : "Not Found");

并将FindUser方法中的代码更改为：

public static User FindUser(User[] users,int noteid)
{       
    foreach (User user in users)                
        if (user.ID == noteid) return user;
    return null;
}

从方法返回用户时看到“UserCustomerNotes.User”输出的原因是：

Console.WriteLine(FindUser(users,noteId));

// instead of

Console.WriteLine(FinderUser(users,noteId).FullName);

因为返回类型是UserCustomerNotes.User并且它没有覆盖“ToString”来指定任何不同的东西,所以当Console.WriteLine询问User对象的文本等效项时给出的默认值是它的名称.这解释了为什么您当前看到代码中的“奇数”输出.

Note: I’ve put Console.WriteLine("The users full name is: {0}",myUserToFind != null ? myUserToFind.FullName : "Not Found"); as your code can return null if it fails to find a user and you’d want to special-case the output you provide in that circumstance.

它也值得一提,但与问题本身无关,格式为：

foreach(var x in y)
    do something;

如果在行下方进行更改,则比在每个语句块周围显式调出{和}时更容易“破坏”：

foreach (User user in users)                
{
    if (user.ID == noteid) 
    {
        return user.FullName;
    }
}
return null;