generics problem

[=?Utf-8?B?QnJpYW4=?=]

I need to write a method that does something like the following. In general
it returns a nullable of the same type as the one passed in. Here is the
problem. If I try to assign a value to the nullable by uncommenting the line
' //tRet = -999;' it won't compile (cannot implicity convert type xxx to T?)
.. Is there a way I can do what I want...perhaps with some reflection method?
If I am heading down the wrong direction with this pleae let me know.

using System;

namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
// should have the (3,3) record in the database at this point...
int? i1 = 10;
int? i1r = (int?)MyMethod(i1);
int? i2 = null;
int? i2r = (int?)MyMethod(i2);
float? f1 = 10f;
float? f1r = (float?)MyMethod(f1);
float? f2 = null;
float? f2r = (float?)MyMethod(f2);
}
private static T? MyMethod<T>(T? myVal) where T : struct
{
try
{
if (myVal.HasValue)
return myVal;

// Now make the constructed type.
Type cType = typeof(Nullable<>).MakeGenericType(typeof(T));
T? tRet = (T?)Activator.CreateInstance(cType);
//tRet = -999;

return tRet;
}
catch
{
return null;
}
}
}
}

[Nicholas Paldino [.NET/C# MVP]]

Brian,

It's not going to work, because 999 is a numeric value, and T can be any
kind of structure (like a DateTime, a TimeSpan) which you can't assign that
value to.

You would have to change your method to take 999 as input, and then
assign it in the method to the parameter passed in:

private static T? MyMethod<T>(T? myVal, T value) where T : struct

--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard.caspershouse.com

"Brian" <Br***@discussions.microsoft.comwrote in message
news:DE**********************************@microsof t.com...

>I need to write a method that does something like the following. In general
it returns a nullable of the same type as the one passed in. Here is the
problem. If I try to assign a value to the nullable by uncommenting the
line
' //tRet = -999;' it won't compile (cannot implicity convert type xxx to
T?)
. Is there a way I can do what I want...perhaps with some reflection
method?
If I am heading down the wrong direction with this pleae let me know.

using System;

namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
// should have the (3,3) record in the database at this
point...
int? i1 = 10;
int? i1r = (int?)MyMethod(i1);
int? i2 = null;
int? i2r = (int?)MyMethod(i2);
float? f1 = 10f;
float? f1r = (float?)MyMethod(f1);
float? f2 = null;
float? f2r = (float?)MyMethod(f2);
}
private static T? MyMethod<T>(T? myVal) where T : struct
{
try
{
if (myVal.HasValue)
return myVal;

// Now make the constructed type.
Type cType = typeof(Nullable<>).MakeGenericType(typeof(T));
T? tRet = (T?)Activator.CreateInstance(cType);
//tRet = -999;

return tRet;
}
catch
{
return null;
}
}
}
}