Reflection - integer values directly to enum

[=?Utf-8?B?dG9iaXdhbl9rZW5vYmk=?=]

The following code is in a custom deserializer:

object value = (int) 1;
string nameToParse = Enum.GetName(fi eld.FieldType, value);
value = Enum.Parse(fiel d.FieldType, nameToParse);

Currently we follow the path below:

intValue --enum name --enum value

Is there any way in reflection to do:

intValue --enum value

[Chris Shepherd]

tobiwan_kenobi wrote:

The following code is in a custom deserializer:

object value = (int) 1;
string nameToParse = Enum.GetName(fi eld.FieldType, value);
value = Enum.Parse(fiel d.FieldType, nameToParse);

Currently we follow the path below:

intValue --enum name --enum value

Is there any way in reflection to do:

intValue --enum value

You can cast to the enum from an int, can't you?

This scenario has always worked for me:
public enum TestEnum
{
One = 1,
Two
}

public TestMyEnum()
{
TestEnum a = (TestEnum)1;
TestEnum b = (TestEnum)2;

Console.WriteLi ne("A: " + a.ToString() + "\nB: " + b.ToString());
}
Chris.

[Jon Skeet [C# MVP]]

Chris Shepherd <ch**@nospam.ch sh.cawrote:

intValue --enum value

You can cast to the enum from an int, can't you?

Only if you know the enum type at compile time - which it looks like
the OP doesn't.

Unfortunately Convert.ChangeT ype doesn't work, which was my first
thought. I suspect that using Expression.Conv ert would work with a bit
of work, but unfortunately dinner is calling me. Time for Marc to take
over, I'd say :)

(Seriously, there must be a better way, but I don't know it offhand...)

--
Jon Skeet - <sk***@pobox.co m>
Web site: http://www.pobox.com/~skeet
Blog: http://www.msmvps.com/jon.skeet
C# in Depth: http://csharpindepth.com

[=?Utf-8?B?dG9iaXdhbl9rZW5vYmk=?=]

No, in this situation we can't cast because we are using reflection to write
a general routine that will create an instance of any enum that needs to get
deserialized, so we don't know which enum it is. The type of enum is
recovered from the XML document at deserialization time.

"Chris Shepherd" wrote:

tobiwan_kenobi wrote:

The following code is in a custom deserializer:

object value = (int) 1;
string nameToParse = Enum.GetName(fi eld.FieldType, value);
value = Enum.Parse(fiel d.FieldType, nameToParse);

Currently we follow the path below:

intValue --enum name --enum value

Is there any way in reflection to do:

intValue --enum value

You can cast to the enum from an int, can't you?

This scenario has always worked for me:
public enum TestEnum
{
One = 1,
Two
}

public TestMyEnum()
{
TestEnum a = (TestEnum)1;
TestEnum b = (TestEnum)2;

Console.WriteLi ne("A: " + a.ToString() + "\nB: " + b.ToString());
}
Chris.

[=?UTF-8?B?TGFzc2UgVsOlZ3PDpnRoZXIgS2FybHNlbg==?=]

tobiwan_kenobi wrote:

No, in this situation we can't cast because we are using reflection to write
a general routine that will create an instance of any enum that needs to get
deserialized, so we don't know which enum it is. The type of enum is
recovered from the XML document at deserialization time.

"Chris Shepherd" wrote:

>tobiwan_keno bi wrote:

>>The following code is in a custom deserializer:

object value = (int) 1;
string nameToParse = Enum.GetName(fi eld.FieldType, value);
value = Enum.Parse(fiel d.FieldType, nameToParse);

Currently we follow the path below:

intValue --enum name --enum value

Is there any way in reflection to do:

intValue --enum value

You can cast to the enum from an int, can't you?

This scenario has always worked for me:
public enum TestEnum
{
One = 1,
Two
}

public TestMyEnum()
{
TestEnum a = (TestEnum)1;
TestEnum b = (TestEnum)2;

Console.WriteLi ne("A: " + a.ToString() + "\nB: " + b.ToString());
}
Chris.

What about:

Object value = (int) 1;
value = Enum.Parse(fiel d.FieldType, value.ToString( ));

--
Lasse Vågsæther Karlsen
mailto:la***@vk arlsen.no
http://presentationmode.blogspot.com/
PGP KeyID: 0xBCDEA2E3

[=?Utf-8?B?dG9iaXdhbl9rZW5vYmk=?=]

Found it. Too easy.

value = Enum.ToObject(f i.FieldType, value);
"tobiwan_kenobi " wrote:

The following code is in a custom deserializer:

object value = (int) 1;
string nameToParse = Enum.GetName(fi eld.FieldType, value);
value = Enum.Parse(fiel d.FieldType, nameToParse);

Currently we follow the path below:

intValue --enum name --enum value

Is there any way in reflection to do:

intValue --enum value

[=?Utf-8?B?dG9iaXdhbl9rZW5vYmk=?=]

"Lasse Vågsæther Karlsen" wrote:

What about:

Object value = (int) 1;
value = Enum.Parse(fiel d.FieldType, value.ToString( ));

Besides not wanting to convert an int to a string to an enum for performance
reasons, it just doesn't work. We tried this and the above would give the
following:

1 --"1" --then fail (because "1" is not one of the names in the enum)

[=?UTF-8?B?TGFzc2UgVsOlZ3PDpnRoZXIgS2FybHNlbg==?=]

tobiwan_kenobi wrote:

>
"Lasse Vågsæther Karlsen" wrote:

>What about:

Object value = (int) 1;
value = Enum.Parse(fiel d.FieldType, value.ToString( ));

Besides not wanting to convert an int to a string to an enum for performance
reasons, it just doesn't work. We tried this and the above would give the
following:

1 --"1" --then fail (because "1" is not one of the names in the enum)

That's odd:

using System;

public class MyClass
{
public enum Test
{
A = 5,
B = 7,
C = 10,
D = 15
}

public static void Main()
{
for (Int32 index = 0; index <= 20; index++)
Console.WriteLi ne(index + " = " + Enum.Parse(type of(Test),
index.ToString( )));
Console.ReadLin e();
}
}

Tested this in Snippet Compiler on .NET 2.0 SP1 and 3.5, and both
produced the following:

0 = 0
1 = 1
2 = 2
3 = 3
4 = 4
5 = A <-- here
6 = 6
7 = B <-- here
8 = 8
9 = 9
10 = C <-- here
11 = 11
12 = 12
13 = 13
14 = 14
15 = D <-- here
16 = 16
17 = 17
18 = 18
19 = 19
20 = 20

As you can see, the enums corresponding to values are correctly parsed
from the string, even though the string is just a number.

In any case, if performance is an issue you won't gain much by mine or
your methods, in both cases you're involving a string.

You can only cast an int to an enum if you know the enum, if all you
have is a Type object, you need to muck about like you or I have done,
and if that doesn't produce fast enough code, well, you're out of luck.

However, let's put aside the current problem for a second.

What specifically is it that you're doing? If you're mucking around with
reflection and custom serialization, are you ultimately going to write
the value into a field or property of that enum type?

In other words, like this?

using System;
using System.Reflecti on;

public class MyClass
{
public enum Test
{
A = 5,
B = 7,
C = 10,
D = 15
}

public Test TestField = Test.D;

public static void Main()
{
MyClass mc = new MyClass();
FieldInfo fi = mc.GetType().Ge tField("TestFie ld");
fi.SetValue(mc, 5);
Console.WriteLi ne(mc.TestField );
Console.ReadLin e();
}
}

The output is A (which corresponds to the 5).

As you can see, I write the integer directly into the property. I assume
some conversion is taking place under the hood, but perhaps this has
less overhead than the code we've looked at so far?

[=?Utf-8?B?dG9iaXdhbl9rZW5vYmk=?=]

Apparently it was different problem. We were reading the information in from
the database and were getting casting errors.

The SetValue using the value from the database was returning a casting
error. SetValue does not give me this error on the value returned from
Enum.ToObject. Since casting values from the database is very picky about
how it is done, Enum.ToObject seems to be the best choice.

"Lasse Vågsæther Karlsen" wrote:

tobiwan_kenobi wrote:

"Lasse Vågsæther Karlsen" wrote:

What about:

Object value = (int) 1;
value = Enum.Parse(fiel d.FieldType, value.ToString( ));

Besides not wanting to convert an int to a string to an enum for performance
reasons, it just doesn't work. We tried this and the above would give the
following:

1 --"1" --then fail (because "1" is not one of the names in the enum)

That's odd:

using System;

public class MyClass
{
public enum Test
{
A = 5,
B = 7,
C = 10,
D = 15
}

public static void Main()
{
for (Int32 index = 0; index <= 20; index++)
Console.WriteLi ne(index + " = " + Enum.Parse(type of(Test),
index.ToString( )));
Console.ReadLin e();
}
}

Tested this in Snippet Compiler on .NET 2.0 SP1 and 3.5, and both
produced the following:

0 = 0
1 = 1
2 = 2
3 = 3
4 = 4
5 = A <-- here
6 = 6
7 = B <-- here
8 = 8
9 = 9
10 = C <-- here
11 = 11
12 = 12
13 = 13
14 = 14
15 = D <-- here
16 = 16
17 = 17
18 = 18
19 = 19
20 = 20

As you can see, the enums corresponding to values are correctly parsed
from the string, even though the string is just a number.

In any case, if performance is an issue you won't gain much by mine or
your methods, in both cases you're involving a string.

You can only cast an int to an enum if you know the enum, if all you
have is a Type object, you need to muck about like you or I have done,
and if that doesn't produce fast enough code, well, you're out of luck.

However, let's put aside the current problem for a second.

What specifically is it that you're doing? If you're mucking around with
reflection and custom serialization, are you ultimately going to write
the value into a field or property of that enum type?

In other words, like this?

using System;
using System.Reflecti on;

public class MyClass
{
public enum Test
{
A = 5,
B = 7,
C = 10,
D = 15
}

public Test TestField = Test.D;

public static void Main()
{
MyClass mc = new MyClass();
FieldInfo fi = mc.GetType().Ge tField("TestFie ld");
fi.SetValue(mc, 5);
Console.WriteLi ne(mc.TestField );
Console.ReadLin e();
}
}

The output is A (which corresponds to the 5).

As you can see, I write the integer directly into the property. I assume
some conversion is taking place under the hood, but perhaps this has
less overhead than the code we've looked at so far?

[=?UTF-8?B?TGFzc2UgVsOlZ3PDpnRoZXIgS2FybHNlbg==?=]

tobiwan_kenobi wrote:

Apparently it was different problem. We were reading the information in from
the database and were getting casting errors.

Then you didn't have an int, you had something else.

This is why it is important for you to post everything you know about a
problem, or, to verify that the code you give us really exhibit the
problems you say it does.

Otherwise we'll post numerous answers or tips which really doesn't help
your real problem at all.

--
Lasse Vågsæther Karlsen
mailto:la***@vk arlsen.no
http://presentationmode.blogspot.com/
PGP KeyID: 0xBCDEA2E3