Question about C# 2.0 generics

[A.M-SG]

Hi,

The following code gives me InvalidCastException with the following message:

{"Unable to cast object of type 'System.Collections.Generic.List`1' to type
'System.Collections.Generic.IList`1'."}

What is the reason?

Any help would be appreciated,

Alan



public OracleDatabase ELOracleDatabase

{

get

{

if (_ELOracleDatabase == null)

{

// ****************************

// InvalidCastException happens here!

IList<IOraclePackage> oraclePackages =
(IList<IOraclePackage>)(new List<OraclePackage>());

_ELOracleDatabase = new OracleDatabase(_connectionString,
null);

}

return _ELOracleDatabase;

}

}

class OraclePackage : IOraclePackage

{

string _name, _prefix;

OraclePackage()

{

_name = string.Empty;

_prefix = string.Empty;

}

public string Name

{

get { return _name; }

set { _name = value; }

}

public string Prefix

{

get { return _prefix; }

set { _prefix = value; }

}

}

public interface IOraclePackage

{

string Name

{ get; }

string Prefix

{ get; }

}

[Christof Nordiek]

'IList<IOraclePackage>' is not a basetype of 'List<OraclePackage>()'
that's all.

[Tim Haughton]

I think you're falling foul of the lack of support for variance in C#. Give
this a read:

http://msdn2.microsoft.com/en-us/library/ms134699

--
Regards,

Tim Haughton

Agitek
http://agitek.co.uk
http://blogitek.com/timhaughton

"A.M-SG" <al******@newsgroup.nospam> wrote in message
news:ed**************@TK2MSFTNGP14.phx.gbl...

Hi,

The following code gives me InvalidCastException with the following message:
{"Unable to cast object of type 'System.Collections.Generic.List`1' to type 'System.Collections.Generic.IList`1'."}

What is the reason?

Any help would be appreciated,

Alan



public OracleDatabase ELOracleDatabase

{

get

{

if (_ELOracleDatabase == null)

{

// ****************************

// InvalidCastException happens here!

IList<IOraclePackage> oraclePackages =
(IList<IOraclePackage>)(new List<OraclePackage>());

_ELOracleDatabase = new OracleDatabase(_connectionString,
null);

}

return _ELOracleDatabase;

}

}

class OraclePackage : IOraclePackage

{

string _name, _prefix;

OraclePackage()

{

_name = string.Empty;

_prefix = string.Empty;

}

public string Name

{

get { return _name; }

set { _name = value; }

}

public string Prefix

{

get { return _prefix; }

set { _prefix = value; }

}

}

public interface IOraclePackage

{

string Name

{ get; }

string Prefix

{ get; }

}