Question

我想将一个数组返回到WP 8页面并出现错误：not all code paths return a value。我该如何纠正？我的WCF服务具有以下代码：

public Point getAllusrs (int myID)
    {
        DataClasses1DataContext data = new DataClasses1DataContext();
        var a = (from s in data.Tabs where s.u1ID == myID && s.status == true select s.u2ID).ToArray();
        int inc = 0;

        foreach (var d in data.Users)
        {
            if (a[inc] != null && d.Id == a[inc])
            {
                inc++;
                return new Point() { Lat = d.usrLat, Lon = d.usrLong };
            }
            else inc++;
        }       
    }

Answer 1

当没有目标为Id的用户时，您必须处理此案例。

例如，您可以在方法的末尾返回默认值：

public Point getAllusrs (int myID)
{
    DataClasses1DataContext data = new DataClasses1DataContext();
    var a = (from s in data.Tabs where s.u1ID == myID && s.status == true select s.u2ID).ToArray();
    int inc = 0;

    foreach (var d in data.Users)
    {
        if (a[inc] != null && d.Id == a[inc])
        {
            inc++;
            return new Point() { Lat = d.usrLat, Lon = d.usrLong };
        }
        else inc++;
    }       
    return default(Point); // or some Point with default Lat and Lon
}

或抛出一些例外：

public Point getAllusrs (int myID)
{
    DataClasses1DataContext data = new DataClasses1DataContext();
    var a = (from s in data.Tabs where s.u1ID == myID && s.status == true select s.u2ID).ToArray();
    int inc = 0;

    foreach (var d in data.Users)
    {
        if (a[inc] != null && d.Id == a[inc])
        {
            inc++;
            return new Point() { Lat = d.usrLat, Lon = d.usrLong };
        }
        else inc++;
    }       
    throw new Exception("Point not found"); // or some custom Exception
}

Answer 2

这是因为如果代码不满足条件，它就不会返回任何值。

public Point getAllusrs (int myID)
{
    Point pnt = null; // or new Point ();
    DataClasses1DataContext data = new DataClasses1DataContext();
    var a = (from s in data.Tabs where s.u1ID == myID && s.status == true select s.u2ID).ToArray();
    int inc = 0;

    foreach (var d in data.Users)
    {
        if (a[inc] != null && d.Id == a[inc])
        {
            inc++;
            pnt = new Point() { Lat = d.usrLat, Lon = d.usrLong };
        }
        else inc++;
    }  

    return pnt;   
}

返回一个LINQ to SQL查询数组

2 个答案: