Re: re-cast of Control back to its Native Type ? - C# Discussion Boards

13-Oct-15 0:48

Windows Forms

Let'say you have a List<Control> : some of those Controls' Native Types have the 'FlatStyle Property; others may have the 'BorderStyle Property; other Controls may have neither. Of course we know that the Button Control, for example, inherits from ButtonBase which inherits from Control, etc.

At run-time we can use reflection to determine if a Control is of a Type that contains a specific Property, and, if the Property exists, get its DeclaringType:

PropertyInfo pif = currentControl.GetType().GetProperty("BorderStyle");

if (pif != null)
{
    Type typ = pif.DeclaringType;
}

If we want to set the 'BorderStyle of the Control at this point, obviously we have to cast it, somehow, back to its Native Type.

But, how ?

thanks, Bill

«I want to stay as close to the edge as I can without going over. Out on the edge you see all kinds of things you can't see from the center» Kurt Vonnegut.

Pete O'Hanlon13-Oct-15 1:14

Pete O'Hanlon

13-Oct-15 1:14

One way I have seen this done, albeit in a hacky way, is to provide a Cast method that looks something like this:

public T Cast<T>(object o)
{
  return (T)o;
}

Then, you call it with this:

MethodInfo methodInfo = this.GetType().GetMethod("Cast").MakeGenericMethod(typ);

You can then choose to do with it, what you will.

modified 13-Oct-15 8:20am.

BillWoodruff13-Oct-15 2:06

13-Oct-15 2:06

Thanks, Pete, I am drawing a blank here about how you would use the 'MethodInfo created in your code. I'm trying this:

// using 'Cast would not compile: name-space clash with Linq ?
public T XCast<T>(object o)
{
    return (T)o;
}

// used like this:

// okay
Type typ = currentControl.GetType(); //.UnderlyingSystemType;

// okay
MethodInfo methodInfo = this.GetType().GetMethod("XCast").MakeGenericMethod(typ);

//  error here: "An unhandled exception of type
// 'System.Reflection.TargetException' occurred in mscorlib.dll
//  Additional information: Object does not match target type."

var xc = methodInfo.Invoke(currentControl, null);

«I want to stay as close to the edge as I can without going over. Out on the edge you see all kinds of things you can't see from the center» Kurt Vonnegut.

Pete O'Hanlon13-Oct-15 2:21

Pete O'Hanlon

13-Oct-15 2:21

Your invoke should look something like this:

methodInfo.Invoke(null, new object[] { button });

But, as Eddy has rightly pointed out - you can always use GetValue and SetValue.

BillWoodruff13-Oct-15 3:01

13-Oct-15 3:01

Thanks, Pete, Eddy's suggestion does enable me to do what I want, but I am still curious about your code; if I use this:

public T XCast<T>(object o) // cannot use the Name 'Cast
{
    return (T)o;
}

// in a code block

PropertyInfo pif = currentControl.GetType().GetProperty("BorderStyle");

if (pif != null)
{
    Type typ = currentControl.GetType(); //.UnderlyingSystemType;
                         
    MethodInfo methodInfo = this.GetType().GetMethod("XCast").MakeGenericMethod(typ);
    
    var xc = methodInfo.Invoke(this, new object[]{currentControl});
}

Then 'xc does appear to have a valid reference to the Control with the BorderStyle Property, but to set that Property: of course, I can't use 'xc.

Is there a "missing piece" of the puzzle here that would let me set the Property without using 'SetValue ?

thanks, Bill

«I want to stay as close to the edge as I can without going over. Out on the edge you see all kinds of things you can't see from the center» Kurt Vonnegut.

Eddy Vluggen13-Oct-15 1:42

Eddy Vluggen

13-Oct-15 1:42

BillWoodruff wrote:
If we want to set the 'BorderStyle of the Control at this point, obviously we have to cast it, somehow, back to its Native Type.

No need to cast, just to get or set the property. If you have the PropertyInfo, then you can call its GetValue method.

Bastard Programmer from Hell Suspicious | :suss:

If you can't read my code, try converting it here[^]

BillWoodruff13-Oct-15 2:18

13-Oct-15 2:18

Excellent, Eddy, as is said in the American South (where I was raised): "if that had been a snake, it would've bit you." Smile | :)

Everytime I make a mistake of omitting to look for the simpler way, I hear the introduction to "Proud Mary" spoken by Tina Turner:

"But there's just one thing
You see we never ever do nothing
Nice, easy"

«I want to stay as close to the edge as I can without going over. Out on the edge you see all kinds of things you can't see from the center» Kurt Vonnegut.

Get rows from database, Entity framework

Eddy Vluggen13-Oct-15 3:41

Eddy Vluggen

13-Oct-15 3:41

Tx, and you're welcome. Just a lucky open spot in the grass where the snake was easy to see Smile | :)

Bastard Programmer from Hell Suspicious | :suss:

If you can't read my code, try converting it here[^]

Member 1204569212-Oct-15 1:49

12-Oct-15 1:49

I have created a .mdf database file. I have created a table and populated It with rows.

Im trying to use Entity framework, to comunicate with the database.

Here, Im using a context to connect to the database:

namespace SportsStore.domain.Concrete
{
    //Associate the model with the database
    //This class then automatically defines a property for each table in the database that I want to work with.
    public class EFDbContext : DbContext
    {
        public DbSet<Product> Products { get; set; }
    }
}

And here, Im trying to get the rows from the database:

namespace SportsStore.domain.Concrete
{
    public class EFProductRepository : IProductRepository
    {
        private EFDbContext context = new EFDbContext();

        public IEnumerable<Product> Products
        {
            get { return context.Products; }
        }
    }
}

When I run my application, nothing Is printed out. The rows from the database are not printed out.

Anyone who can help me with this? Should I add something to Web.Config? If so, what should I add?

Dave Kreskowiak12-Oct-15 4:36

12-Oct-15 4:36

You haven't shown all the relevant code so it's impossible to be sure why it's not working.

But, I will say that your repository code doesn't return an IEnumerable<Product>. Your code is actually returning a DbSet<Product>, which just so happens to implement IEnumberable<TEntity> so the code doesn't throw an error when you compile it.

The set you're returning is empty because the query hasn't actually run. You have to call some method on the Products query, typically .ToList(), to force the query to run and build the list in memory. It's called "deferred execution[^]". If you're using Entity Framework you better understand what this is.

Your repository should looks more like this:

namespace SportsStore.domain.Concrete
{
    public class EFProductRepository : IProductRepository
    {
        private EFDbContext context = new EFDbContext();
 
        public IEnumerable<Product> Products
        {
            get { return context.Products.ToList(); }
        }
    }
}

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Dave Kreskowiak

Member 1204569212-Oct-15 4:48

12-Oct-15 4:48

Sorry. That did not help me. Someone else?` Smile | :)

Dave Kreskowiak12-Oct-15 4:50

12-Oct-15 4:50

Lie I said, you have not supplied all the relevant code, such as your View and Controller code.

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Dave Kreskowiak

Member 1204569212-Oct-15 5:09

12-Oct-15 5:09

When I add ToList(), I get the following error:

Additional information: Failed to set database initializer of type 'SportsStore.domain.Concrete, EFProductRepository' for DbContext type 'SportsStore.domain.Concrete, EFDbContext' specified in the application configuration. See inner exception for details.

Does this mean that I have to add a line to my Web.Config file?

Dave Kreskowiak12-Oct-15 5:14

12-Oct-15 5:14

And the inner exception message is .......?

Also, what IS in your Web.Config file?

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Dave Kreskowiak

Member 1204569212-Oct-15 9:35

12-Oct-15 9:35

The message of my inner exception says: "Can not load file or assembly EFDbContext or one of its dependencies. The system can not find the file EFDbContext"

Here is my Web.Config:

XML

<?xml version="1.0" encoding="utf-8"?>
<!--
  For more information on how to configure your ASP.NET application, please visit
  http://go.microsoft.com/fwlink/?LinkId=301880
  -->
<configuration>
  <configSections>
    <section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
  <!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 --></configSections>
  <appSettings>
    <add key="webpages:Version" value="3.0.0.0" />
    <add key="webpages:Enabled" value="false" />
    <add key="ClientValidationEnabled" value="true" />
    <add key="UnobtrusiveJavaScriptEnabled" value="true" />
  </appSettings>
  <system.web>
    <compilation debug="true" targetFramework="4.5.2" />
    <httpRuntime targetFramework="4.5.2" />
  </system.web>
  <runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <dependentAssembly>
        <assemblyIdentity name="System.Web.Helpers" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="1.0.0.0-3.0.0.0" newVersion="3.0.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Web.WebPages" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="1.0.0.0-3.0.0.0" newVersion="3.0.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Web.Mvc" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="0.0.0.0-5.2.3.0" newVersion="5.2.3.0" />
      </dependentAssembly>
    </assemblyBinding>
  </runtime>
  <system.codedom>
    <compilers>
      <compiler language="c#;cs;csharp" extension=".cs" type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.CSharpCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" warningLevel="4" compilerOptions="/langversion:6 /nowarn:1659;1699;1701" />
      <compiler language="vb;vbs;visualbasic;vbscript" extension=".vb" type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.VBCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" warningLevel="4" compilerOptions="/langversion:14 /nowarn:41008 /define:_MYTYPE=\"Web\" /optionInfer+" />
    </compilers>
  </system.codedom>
  <entityFramework>

    <contexts>
      <context type="SportsStore.domain.Concrete, EFDbContext">
        <databaseInitializer type="SportsStore.domain.Concrete, EFProductRepository" />
      </context>
    </contexts>
    <defaultConnectionFactory type="System.Data.Entity.Infrastructure.LocalDbConnectionFactory, EntityFramework">
      <parameters>
        <parameter value="mssqllocaldb" />
      </parameters>
    </defaultConnectionFactory>
    <providers>
      <provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" />
    </providers>
  </entityFramework>
</configuration>

Dave Kreskowiak12-Oct-15 9:54

12-Oct-15 9:54

Your <context> and <databaseInitializer> lines are wrong. They're saying "look for a class called 'SportsStore.domain.Concrete' in the assembly 'EFProductRepository' in one line and in 'EFProductRepository' in the other. That's not what the class is called nor where to find it.

I think it should be more like:

<contexts>
  <context type="SportsStore.domain.Concrete.EFDbContext, assemblyNameGoesHere!">
    <databaseInitializer type="SportsStore.domain.Concrete.initializerClassNameGoesHere, assemblyNameGoesHere!" />
  </context>
</contexts>

It's impossible to provide the exact names because you haven't provided enough information. But, you have to fill in the missing initializer class name that you wrote to initialize the database and the assembly names that contain the specified classes.

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Dave Kreskowiak

Member 1204569212-Oct-15 10:30

12-Oct-15 10:30

And what Is assemblyNameGoesHere and initializerClassName?

What kind of more information do you need?

Dave Kreskowiak12-Oct-15 10:33