Assigning a type .net

Question

Type T;

if (report.ReportType == 0) {
    T = typeof(ReportTempHum);
} else if (report.ReportType == 11){
    T = typeof(ReportVibration);
}

List<(Type)T> result = new List<(Type)T>();

I'm trying to assign a type into a List in terms of a reportType condition. But some errors.

How can I do this ?

Thanks in Advance!

Edit: Error; Severity Code Description Project File Line Suppression State Error CS0118 'T' is a variable but is used like a type

What error are you getting and what exactly are you trying to achieve? — npinti, Jan 16 '17 at 08:07
I've answered with what seems to me to be the most likely issue, but will adjust if you provide the error — ScottishTapWater, Jan 16 '17 at 08:09
Please see my answer, after a bit of digging I don't think this can be done unless you do something like @OriNachum's answer, resort to dynamics, or use reflection to generate your new classes OTF. — ScottishTapWater, Jan 16 '17 at 08:21

score 4 · Accepted Answer · answered Jan 16 '17 at 08:12

4

Make sure ReportTempHum and ReportVibration have the same interface.

List<IReportType> result;
        if (report.ReportType == 0) {
            result = new List<ReportTempHum>();
        } else if (report.ReportType == 11){
            result = new List<ReportVibration>();
        }

        //note to verify List is not null!

answered Jan 16 '17 at 08:12

Ori Nachum

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Might be worth switching on the `report.ReportType` if there are many options too. – ScottishTapWater Jan 16 '17 at 08:14
Yes. That's another way to solve the problem. But I am looking for a solution by using the "Type". Thank you. – NewPHPer Jan 16 '17 at 08:14
Try using object (Or other closest class) then, and every time you work with the list's data, cast it to T. – Ori Nachum Jan 16 '17 at 08:46
1

@NewPHPer _But I am looking for a solution by using the "Type"_ you are trying to solve a problem in wrong way. why not use polymorphism which is most important thing in OOP, even name of your classes are telling they must have same base like `Report` class – M.kazem Akhgary Jan 16 '17 at 09:14

score 2 · Answer 2 · edited May 23 '17 at 12:02

2

I'm afraid this can't be done:

The whole point of generics is to provide compile-time safety. Consequently, type objects cannot be used as generic parameters.

Please see answer here for more information.

edited May 23 '17 at 12:02

Community

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1

answered Jan 16 '17 at 08:09

ScottishTapWater

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In his case `T` is a Type object, which you cannot use as a generic type parameter. – GWigWam Jan 16 '17 at 08:11

score 0 · Answer 3 · answered Jan 16 '17 at 09:35

With this code you can get a List of Type T. However, keep in mind it isn't strongly typed!

Type T;

if (report.ReportType == 0) {
    T = typeof(ReportTempHum);
} else if (report.ReportType == 11){
    T = typeof(ReportVibration);
}

var constructedListType = typeof(List<>).MakeGenericType(T);
var instance = Activator.CreateInstance(constructedListType);

score -1 · Answer 4 · edited May 23 '17 at 10:29

-1

Just use dynamic as the argument:

var result = new List<dynamic>();

For more inframtion see: https://msdn.microsoft.com/en-us/library/dd264736.aspx

See also this related question: How to create a List with a dynamic object type C#

edited May 23 '17 at 10:29

Community

1
1

answered Jan 16 '17 at 08:19

George Mamaladze

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Downvoted. Usually if you have to use `dynamic` your program design is usually wrong. `dynamic` was not invented to be used in regular C# code. Generally it should only be used when working with COM, dynamic typed language libraries, ASP.NET MVC views etc. not something like this. – Bauss Jan 16 '17 at 14:30

Assigning a type .net

4 Answers4