Using Switch case with Equals method in C#

Question

Is there a way to convert the below if else condition into Switch in C#. I am using Equals method for checking the type, but unable to convert to switch case.

if (fi.FieldType.Equals(typeof(int)))
{
    fi.SetValue(data, BitConverter.ToInt32(buffer, 0));
}
else if (fi.FieldType.Equals(typeof(bool)))
{
    fi.SetValue(data, BitConverter.ToBoolean(buffer, 0));
}
else if (fi.FieldType.Equals(typeof(string)))
{
    byte[] tmp = new byte[la.length];
    Array.Copy(buffer, tmp, tmp.Length);
    fi.SetValue(data, System.Text.Encoding.UTF8.GetString(tmp));
}
else if (fi.FieldType.Equals(typeof(double)))
{
    fi.SetValue(data, BitConverter.ToDouble(buffer, 0));
}
else if (fi.FieldType.Equals(typeof(short)))
{
    fi.SetValue(data, BitConverter.ToInt16(buffer, 0));
}

Please help us....

You can see an example of c# pattern matching here: https://stackoverflow.com/a/44447980/1736047 — STLDev, Apr 18 '18 at 12:42
if C# 7 the use pattern expression matching `https://learn.microsoft.com/en-us/dotnet/csharp/pattern-matching` Or below then convert the typeof(type) to string and match with string representation of fi.FieldType — user1672994, Apr 18 '18 at 12:43
@TimSchmelter there's no need for pattern matching, the code checks the *value* of `FieldType`. A common switch would work. — Panagiotis Kanavos, Apr 18 '18 at 12:44
@PanagiotisKanavos But the compiler will complain that you need to use a constant value if you try to compare it with `typeof(x)` — DavidG, Apr 18 '18 at 12:46
@Bhrathi *why* are you doing this anwyay? This looks like reflection code. Are you trying to deserialize something? There may already be a built-in implementation for what you want — Panagiotis Kanavos, Apr 18 '18 at 12:54

score 11 · Answer 1 · answered Apr 18 '18 at 12:43

11

With C# 7 pattern matching you can do this:

switch (fi.FieldType)
{
    case var _ when fi.FieldType.Equals(typeof(int)):
        fi.SetValue(data, BitConverter.ToInt32(buffer, 0));
        break;
    case var _ when fi.FieldType.Equals(typeof(bool)):
        fi.SetValue(data, BitConverter.ToBoolean(buffer, 0));
        break;

    //etc
}

Note that this is using _ to discard the value as we don't care about it.

answered Apr 18 '18 at 12:43

DavidG

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Thanks for quick reply. – Bhrathi Apr 18 '18 at 12:48
You could use [Type.GetTypeCode](https://msdn.microsoft.com/en-us/library/system.type.gettypecode(v=vs.110).aspx) and use a switch with earlier versions too – Panagiotis Kanavos Apr 18 '18 at 12:48
@Bhrathi this looks like reflection code. What are you really trying to do? There may be an implementation for this already – Panagiotis Kanavos Apr 18 '18 at 12:49
@PanagiotisKanavos Yes, that's assuming they're all CLR types of course – DavidG Apr 18 '18 at 12:50
@DavidG that's a safe assumption in this case. BitConverter doesn't even support *all* base types – Panagiotis Kanavos Apr 18 '18 at 12:52
@PanagiotisKanavos Well possibly safe, but I don't like making assumptions if I can help it. There's no reason why OP may not add a new case in the future which is some DTO for example. – DavidG Apr 18 '18 at 12:54
While this is technically using a `switch`, you're still using it as if it were an `if else` chain. `fi.FieldType` in `switch (fi.FieldType)` is unused, you could put literally any value there. You're only using the `when boolean_evaluation` part, which is no different from `if(boolean_evaluation)`. This is one of those cases where you're changing the syntax to fit with the proposed change, while ignoring the actual underlying reason why the change is needed. – Flater Apr 18 '18 at 12:58
@PanagiotisKanavos Thanks for your comments. I will check with Type.GetTypeCode.. Actually I need to convert into switch case as per code review comments.. – Bhrathi Apr 18 '18 at 12:59
@DavidG there are too many assumptions in this question already. This is reflection code, possibly for deserialization. Something that works without pattern matching or even `switch`. – Panagiotis Kanavos Apr 18 '18 at 13:00

Using Switch case with Equals method in C#

1 Answers1