我们如何键入强制转换 IEnumerable <keyvaluepair<string, ienumerable<classa> &gt;&gt; objOld 变成 IEnumerable <keyvaluepair<string, ienumerable<classb> &gt;&gt; 新对象？ </keyvaluepair<string,></keyvaluepair<string,>

Question

I have an object IEnumerable<KeyValuePair<string, IEnumerable<ClassA>>> objOld; which i want to cast into IEnumerable<KeyValuePair<string, IEnumerable<ClassB>>> objNew; .

ClassA and ClassB both have same objects

public class ClassA
{ `public string str1 { get; set; }
    public string str2 { get; set; } 
    public int newNum { get; set; } `
}

public class ClassB
{ `public string str1 { get; set; }
    public string str2 { get; set; } 
    public int newNum { get; set; } `
}

I tried following but it is generating exception.

objNew = objOld.Cast<IEnumerable<KeyValuePair<string, IEnumerable<ClassB>>>>();

Please let me know possible ways to do so.

Answer 1

Only because two classes have the same members does not imply any inheritance-relation. Instead of casting one to the other you should create new instances of B for every A .

var result = myInput.ToDictionary(x => x.Key, x => x.Select(y => new ClassB { 
        str1 = y.str1, 
        str2 = y.str2, 
        newNum = y.newNum 
    })
);

Or if you really want a list of KeyValuePair :

var result = myInput.Select(x => 
    new KeyValuePair<string, IEnumerable<ClassB>>(x.Key, x => x.Select(y => new ClassB { 
        str1 = y.str1, 
        str2 = y.str2, 
        newNum = y.newNum 
    })
));

Answer 2

You should use Select method twice for that. First time to map every KeyValuePair to new one, second time to map internal IEnumerable<ClassA> to IEnumerable<ClassB> . There is no way to directly cast ClassA instance to ClassB , because classes are different. So, you should create ClassB instance manually based on properties of every ClassA instance

IEnumerable<KeyValuePair<string, IEnumerable<ClassB>>> objNew = objOld.Select(o =>
    new KeyValuePair<string, IEnumerable<ClassB>>(o.Key, o.Value.Select(a => new ClassB
    {
        str1 = a.str1,
        str2 = a.str2,
        newNum = a.newNum
    })));