The Wiert Corner – irregular stream of stuff

Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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Archive for the ‘.NET’ Category

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PowerShell aliases (via: Top Ten PowerShell Aliases for DOS Commands)

Posted by jpluimers on 2014/02/26

In most programming environments, I tend to avoid abbreviations, especially since command-completion and parameter-completion makes it easier to write readable code.

Same fore PowerShell: the PowerShell ISE has great completion features.

Other people tend to use abbreviations, especially since many PowerShell aliases make it easier for people coming from a cmd or bash background.

Two Get-Alias commands I use quite often for researching aliases:

  • Get-Alias -Definition <name>
  • Get-Alias | Sort-Object Definition

The former gives you the CmdLet for an alias.
The latter all defines alises sorted by the CmdLet definition.

Two aliases that I tend to avoid are these:

While you are at it, there are also parameter aliases. Read Weekend Scripter: Discovering PowerShell Cmdlet Parameter Aliases on TechNet Blogs to learn more about these.

–jeroen

via: Top Ten PowerShell Aliases for DOS Commands.

Posted in .NET, CommandLine, Development, PowerShell, Software Development | Leave a Comment »

Genymotion (formerly AndroVM) is an Android x86 virtual machine appliance (via: install in VMware Player/Workstation – YouTube)

Posted by jpluimers on 2014/02/14

Very interesting: Install AndroVM in VMware Player/Workstation – YouTube.

The successor is Genymotion “the faster Android emulator”, and seems to have an easier installation path: Run Android on Your Desktop With Genymotion Android Emulator.

One of the drawbacks of going native: the Delphi for Android compiler currently only generates ARM Android code, otherwise this would be a great way to test your apps.

But it works fine if you use Java, Oxygene for Java or MonoDroid: much faster than the emulator (which you cannot run in a VM at all).

There seems to be a way to install ARM translation, so I need to check that out: android – How to install google play service in the genymotion (ubuntu 13.04) .Currently it doesn’t have drag and drop suport – Stack Overflow.

–jeroen

via: Koushik Dutta – Google+ – Even if Microsoft is considering supporting Android apps on….

Posted in .NET, Android, Android Devices, Delphi, Delphi XE5, Development, Mobile Development, Mono for Android, Power User, Software Development | Tagged: , | 4 Comments »

ManagedSpy now maintained by ForNeVeR (via: managed – What happened to ManagedSpy?)

Posted by jpluimers on 2014/02/13

ForNeVeR now maintains ManagedSpy, see his answer on StackOverflow

BTW, I’ve cloned the original ManagedSpy source code and maintaining the code today (for example, ported it to .NET4).

See project on GitHub.

–jeroen

via: managed – What happened to ManagedSpy? – Stack Overflow.

Posted in .NET, .NET 4.0, .NET 4.5, C#, C# 4.0, C# 5.0, Development, Software Development | Leave a Comment »

.NET/C#: DBNull explained

Posted by jpluimers on 2014/02/11

The DBNull type is a very special type in .NET. It represents null values in databases, which are slightly different than null values in .NET.

The biggest confusion that people have with it is that it won’t convert to anything. Which means that you see a lot of questions like “System.InvalidCastException: Conversion from type ‘DBNull’ to type” “is not valid”.

You’d think the full name would be System.Data.DBNull, it is actually named System.DBNull. The reason is that various other functionality of the System namespace depend on it, for instance the System.Convert class.

DBNull was already present in .NET 1.x, so it predates nullable types that were introduced in C# 2 / .NET 2.

A null value on the database side will result in a DBNull instance.

If you want to explicitly pass a null value to a database, you use a DBNull.Value, which is a singleton.

Why DBNull

There is a very interestin question/answer series on StackOverflow about this: via .net – What is the point of DBNull? – Stack Overflow.

There are a few good arguments both for and against DBNull.

But the baseline is that DBNull predates the introduction in the .NET framework of genuine nullable types. Both their behaviour is slightly different, so DBNull had to stay.

Which means you have to deal with it every now and then.

Invalid casts

A bit more background on the invalid casts.

It is thrown like this:

            throw new InvalidCastException(Environment.GetResourceString("InvalidCast_DBNull"));

from

Convert.DefaultToType();

which is called from the DBNull method

    object IConvertible.ToType(Type type, IFormatProvider provider);

All other IConvertible methods are implementated like

bool IConvertible.ToBoolean(IFormatProvider provider)
{
    throw new InvalidCastException(Environment.GetResourceString("InvalidCast_FromDBNull"));
}

So these all throw the same exception:

    bool IConvertible.ToBoolean(IFormatProvider provider);
    byte IConvertible.ToByte(IFormatProvider provider);
    char IConvertible.ToChar(IFormatProvider provider);
    DateTime IConvertible.ToDateTime(IFormatProvider provider);
    decimal IConvertible.ToDecimal(IFormatProvider provider);
    double IConvertible.ToDouble(IFormatProvider provider);
    short IConvertible.ToInt16(IFormatProvider provider);
    int IConvertible.ToInt32(IFormatProvider provider);
    long IConvertible.ToInt64(IFormatProvider provider);
    sbyte IConvertible.ToSByte(IFormatProvider provider);
    float IConvertible.ToSingle(IFormatProvider provider);
    ushort IConvertible.ToUInt16(IFormatProvider provider);
    uint IConvertible.ToUInt32(IFormatProvider provider);
    ulong IConvertible.ToUInt64(IFormatProvider provider);

–jeroen

via:

Posted in .NET, .NET 1.x, .NET 2.0, .NET 3.0, .NET 3.5, .NET 4.0, .NET 4.5, C#, C# 1.0, C# 2.0, C# 3.0, C# 4.0, C# 5.0, Development, Software Development | Leave a Comment »

.NET/C#: When XmlSerializer throws “Unable to generate a temporary class (result=1).” / “error CS2001”

Posted by jpluimers on 2014/02/06

A while ago, I had this error when running an application on a hardened server:

Unhandled Exception:System.InvalidOperationException:
Unable to generate a temporary class (result=1).
error CS2001: Source file 'C:\windows\TEMP\0hocq2nq.0.cs' could not be found  error CS2008: No inputs specified
at System.Xml.Serialization.Compiler.Compile(Assembly parent, String ns, XmlSerializerCompilerParameters xmlParameters, Evidence evidence)
at System.Xml.Serialization.TempAssembly.GenerateAssembly(XmlMapping[] xmlMappings, Type[] types, String defaultNamespace, Evidence evidence, XmlSerializerCompilerParameters parameters, Assembly assembly, Hashtable assemblies)
at System.Xml.Serialization.TempAssembly..ctor(XmlMapping[] xmlMappings, Type[] types, String defaultNamespace, String location, Evidence evidence)
at System.Xml.Serialization.XmlSerializer..ctor(Type type, XmlAttributeOverrides overrides, Type[] extraTypes, XmlRootAttribute root, String defaultNamespace, String location, Evidence evidence)
at System.Xml.Serialization.XmlSerializer..ctor(Type type, XmlAttributeOverrides overrides, Type[] extraTypes, XmlRootAttribute root, String defaultNamespace, String location)
at System.Xml.Serialization.XmlSerializer..ctor(Type type, Type[] extraTypes)

Usually I’m not the first with strange errors, but searching for “Unhandled Exception:System.InvalidOperationException: Unable to generate a temporary class” didn’t get many results.

This was a program running from SSIS under a non-system domain account with very little access.

My first guess was the right now: the XmlSerializer wants to generate a temporary C# file, then compile it into a temporary assembly. Since it cannot generate the C# file because the account does not have access to %windir\TEMP%, the compiler cannot find the (not generated) C# file.

After a few tries, I searched for XmlSerializer without GenerateAssembly, where the first hit ended at Changing where XmlSerializer Outputs Temporary Assemblies – Scott Hanselman.

That post indicated I should try looking for tempFilesLocation in the XmlSerializer context.

That got me these posts: Read the rest of this entry »

Posted in .NET, .NET 1.x, .NET 2.0, .NET 3.0, .NET 3.5, .NET 4.0, .NET 4.5, C#, C# 1.0, C# 2.0, C# 3.0, C# 4.0, C# 5.0, Development, Software Development | Leave a Comment »

.NET/C#/VB.NET – Default value for generics (via: Stack Overflow)

Posted by jpluimers on 2014/02/05

Looking for the pesky little differences between C# and VB.NET, I stumbled over this nice question by Micah Martin on default values for generics in VB.NET as compared to C#. Actually there were 3 questions, so I did a bit of post-editing:

How do I create the default for a generic in VB.NET? in C# I can call:
T variable = default(T);

  1. How do I do this in VB?
  2. If this just returns null (C#) or nothing (VB.NET) then what happens to value types?
  3. Is there a way to specify for a custom type what the default value is? For instance what if I want the default value to be the equivalent to calling a parameterless constructor on my class.

User Konrad Rudolph – Stack Overflow. promptly gave three answers:

Question 1:

Dim variable As T ‘ or ‘ Dim variable As T = Nothing ‘ or ‘ Dim variable As New T() Notice that the latter only works if you specifiy either the New or the Structure constraint for the generic type.

Question 2:

For value types all members of the struct are “nulled” out, i.e. all reference type members are set to null (Nothing) and all value types are in turn nulled out. And no, since string is a reference type, it does not result in "" for strings as suggested in the other answer.

Question 3:

No, there’s no way to specify this. There are some threads about this on Stack Overflow already, e.g. here. Jon has posted an excellent explanation why this is.

–jeroen

via: c# – Default value for generics – Stack Overflow.

Posted in .NET, .NET 1.x, .NET 2.0, .NET 3.0, .NET 3.5, .NET 4.0, .NET 4.5, C#, C# 1.0, C# 2.0, C# 3.0, C# 4.0, C# 5.0, Development, Software Development, VB.NET, VB.NET 10.0, VB.NET 11.0, VB.NET 7.0, VB.NET 7.1, VB.NET 8.0, VB.NET 9.0 | Leave a Comment »

.NET/C#: refactoring some C# 1 code that uses HashTables as a poor mans property bag (via:Stack Overflow)

Posted by jpluimers on 2014/01/30

A while ago, I was refactoring some C# 1 code that uses HashTables as a poor mans property bag.

The problem was that I felt my code was convoluted, and should be denser, especially avoiding Convert.ChangeType. My code was already much simpler than casting tuples to a superclass.

So I asked this question on StackOverflow: c# – Is there a solution that feels less clumsy than Convert.ChangeType to get the value from a HashTable – Stack Overflow.

User dasblinkenlight showed it could be shortened and explained why (hyperlinks are mine):

Since System.String is sealed, the expression

genericType.IsSubclassOf(stringType)

is the same as

genericType == stringType

Therefore you do not need a call of Convert.ChangeType: you can cast to T by casting to object, like this:

object stringResult; // Note the change of type to "object"
if (haveValue)
    stringResult = ((string)properties[propertyName]).Trim();
else
    stringResult = string.Empty;
result = (T)stringResult; // It is allowed to cast object to generic T

The original .NET 1.1 code had loads of null checks wrapped if/then/else statements to assign default values for null values.
I wanted to get rid of that, and get code like this: Read the rest of this entry »

Posted in .NET, .NET 1.x, .NET 2.0, .NET 3.0, .NET 3.5, .NET 4.0, .NET 4.5, C#, C# 1.0, C# 2.0, C# 3.0, C# 4.0, C# 5.0, Development, Software Development | Leave a Comment »

.NET/C#: fun with enums and aliases part 2

Posted by jpluimers on 2014/01/29

In the .NET/C#: fun with enums and aliases part 1 you saw that an enumerated type can specify an underlying type.

The underlying type is limited to a strict set of built-in C# types: , so you cannot use a CTS type for it.

So you might think that you can only define enumeration values by integer constant like this:

namespace BeSharp
{
    enum TwoState
    {
        False = 0,
        True = 1,
    }
    enum ThreeState
    {
        False = 0,
        True = 1,
        Unknown = -1,
    }
}

Well, you can do it like this too, since Operations between different enum types are allowed in another enum declaration: Read the rest of this entry »

Posted in .NET, .NET 1.x, .NET 2.0, .NET 3.0, .NET 3.5, .NET 4.0, .NET 4.5, C#, C# 1.0, C# 2.0, C# 3.0, C# 4.0, C# 5.0, Development, Software Development | Leave a Comment »

.NET/C#: an alias is not the same as a synonym: int versus Int32, etc (fun with enums and aliases part 1)

Posted by jpluimers on 2014/01/28

I was amongst the C# programmers that believe the below table of C# integral types is an alias table. But it is not: it is a synonym table.

C# type .NET Framework Type/
Common Type System
byte System.Byte
sbyte System.SByte
short System.Int16
ushort System.UInt16
int System.Int32
uint System.UInt32
long System.Int64
ulong System.UInt64

You can use the common type system types as coding standard, or prefer the C# types. There are arguments for both.

I am still in the first group: prefer CTS types. They make changing between .NET languages a lot easier (C# and VB.NET are not the only .NET based CLI languages I use).

And indeed almost everywhere you can exchange the .NET Framework Type and the C# type without changing meaning.

There are two exceptions Read the rest of this entry »

Posted in .NET, C#, Delphi, Development, Jon Skeet, Software Development | 1 Comment »

Faking num lock, caps lock and scroll lock leds – About My Code

Posted by jpluimers on 2014/01/21

I remember doing this in DOS ages ago (in the Turbo Pascal 5 era) for exactly the same reason: flash the keyboard LEDs to indicate some event was happening, but I’ve yet to find back the source code.

Here is how to do it in Windows using either C# or C: Faking num lock, caps lock and scroll lock leds – About My Code.

–jeroen

via: c# – Way to turn on keyboard’s caps-lock light without actually turning on caps-lock? – Stack Overflow.

Posted in .NET, .NET 1.x, .NET 2.0, .NET 3.0, .NET 3.5, .NET 4.0, .NET 4.5, C, C#, C# 1.0, C# 2.0, C# 3.0, C# 4.0, C# 5.0, C++, Development, Pascal, Software Development, Turbo Pascal | Leave a Comment »

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