    using System.ComponentModel;

    TypeConverter typeConverter = TypeDescriptor.GetConverter(propType);
    object propValue = typeConverter.ConvertFromString(inputValue);

Try [Convert.ChangeType][1]

    object propvalue = Convert.ChangeType(inputValue, propType);


  [1]: http://msdn.microsoft.com/en-us/library/system.convert.changetype%28VS.100%29.aspx

I don&#39;t really think I understand what your are trying to archieve, but.. you mean a dynamic casting? Something like this:

     TypeDescriptor.GetConverter(typeof(String)).ConvertTo(myObject, typeof(Program));

Cheers.

I&#39;m working on a iPhone app which has a pretty large UITableView with data taken from the web, so I&#39;m trying to optimize its creation and usage.


I found out that `dequeueReusableCellWithIdentifier` is pretty useful, but after seeing many source codes using this, I&#39;m wondering if the usage I make of this function is the good one.

Here is what people usually do:

    UITableViewCell* cell = [tableView dequeueReusableCellWithIdentifier:@&quot;Cell&quot;];
   
    if (cell == nil) {
      cell = [[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:@&quot;Cell&quot;];
    
    // Add elements to the cell
    return cell;

And here is the way I did it:

    // The cell row
    NSString identifier = [NSString stringWithFormat:@&quot;Cell %d&quot;, indexPath.row]; 
    
    UITableViewCell* cell = [tableView dequeueReusableCellWithIdentifier:identifier];

    if (cell != nil)
      return cell;

    cell = [[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:identifier];
    // Add elements to the cell
    return cell;

The difference is that people use the same identifier for every cell, so dequeuing one only avoids to alloc a new one.

For me, the point of queuing was to give each cell a unique identifier, so when the app asks for a cell it already displayed, neither allocation nor element adding have to be done.

&lt;i&gt;In fine&lt;/i&gt; I don&#39;t know which is best, the &quot;common&quot; method ceils the table&#39;s memory usage to the exact number of cells it display, whilst the method I use seems to favour speed as it keeps all calculated cells, but can cause large memory consumption (unless there&#39;s an inner limit to the queue).

Am I wrong to use it this way? Or is it just up to the developer, depending on his needs?

iPhone - dequeueReusableCellWithIdentifier usage

How can I undo the most recently executed mysql query?

How can I undo a mysql statement that I just executed?

I want to convert a string to a generic type

I have this:

    string inputValue = myTxtBox.Text;    

    PropertyInfo propInfo = typeof(MyClass).GetProperty(myPropertyName);
    Type propType = propInfo.PropertyType;
    
    object propValue = ?????

I want to convert &#39;inputString&#39; to the type of that property, to check if it&#39;s compatible
how can I do that?

tks 

How to convert string to any type

I want to convert a string to a generic type
I have this:
<pre><code class="hljs language-ini">string inputValue = myTxtBox.Text; 

PropertyInfo propInfo = typeof(MyClass).GetProperty(myPropertyName);
Type propType = propInfo.PropertyType;

object propValue = ?????
</code></pre>
I want to convert 'inputString' to the type of that property, to check if it's compatible
how can I do that?
tks

There are a few minor places where code for my project may be able to be drastically improved if the target framework were a newer version. I&#39;d like to be able to better leverage conditional compilation in C# to switch these as needed.

Something like:

    #if NET40
    using FooXX = Foo40;
    #elif NET35
    using FooXX = Foo35;
    #else NET20
    using FooXX = Foo20;
    #endif

Do any of these symbols come for free? Do I need to inject these symbols as part of the project configuration? It seems easy enough to do since I&#39;ll know which framework is being targeted from MSBuild.

    /p:DefineConstants=&quot;NET40&quot;

How are people handling this situation? Are you creating different configurations? Are you passing in the constants via the command line?



Conditional compilation and framework targets

I wanted to track the performance of my code so I stored the start and end time using `System.DateTime.Now`. I took the difference between the two as the time my code to execute. 

I noticed though that the difference didn&#39;t appear to be accurate. So I tried using a `Stopwatch` object. This turned out to be much, much more accurate.

Can anyone tell me why `Stopwatch` would be more accurate than calculating the difference between a start and end time using `System.DateTime.Now`?

BTW, I&#39;m not talking about a tenths of a percent. I get about a 15-20% difference.

Stopwatch vs. using System.DateTime.Now for timing events

As the title says, I am getting: 

&gt; Invalid length for a Base-64 char
&gt; array.

I have read about this problem on here and it seems that the 
suggestion is to store ViewState in SQL if it is large. I am 
using a wizard with a good deal of data collection so chances
are my ViewState is large. But, before I turn to the &quot;store-in-DB&quot;
solution, maybe somebody can take a look and tell me if I have 
other options?

I construct the email for delivery using the below method:

    public void SendEmailAddressVerificationEmail(string userName, string to)
    {
        string msg = &quot;Please click on the link below or paste it into a browser to verify your email account.&lt;BR&gt;&lt;BR&gt;&quot; +
                        &quot;&lt;a href=\&quot;&quot; + _configuration.RootURL + &quot;Accounts/VerifyEmail.aspx?a=&quot; +
                        userName.Encrypt(&quot;verify&quot;) + &quot;\&quot;&gt;&quot; +
                        _configuration.RootURL + &quot;Accounts/VerifyEmail.aspx?a=&quot; +
                        userName.Encrypt(&quot;verify&quot;) + &quot;&lt;/a&gt;&quot;;

        SendEmail(to, &quot;&quot;, &quot;&quot;, &quot;Account created! Email verification required.&quot;, msg);
    }

The Encrypt method looks like this: 

    public static string Encrypt(string clearText, string Password)
    {
     
        byte[] clearBytes = System.Text.Encoding.Unicode.GetBytes(clearText);

        PasswordDeriveBytes pdb = new PasswordDeriveBytes(Password, new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });

     
        byte[] encryptedData = Encrypt(clearBytes, pdb.GetBytes(32), pdb.GetBytes(16));

        return Convert.ToBase64String(encryptedData);
    }

Here is what the HTML looks like in hotmail:

&gt; Please click on the link below or
&gt; paste it into a browser to verify your
&gt; email account.
&gt; 
&gt; http://localhost:1563/Accounts/VerifyEmail.aspx?a=YOHY57xYRENEOu3H+FGq1Rf09AZAI56EPjfwuK8XWKg=

On the receiving end, the VerifyEmail.aspx.cs page has the line:

     string username = Cryptography.Decrypt(_webContext.UserNameToVerify, &quot;verify&quot;);

Here is the getter for UserNameToVerify:

    public string UserNameToVerify
    {
        get
        {
            return GetQueryStringValue(&quot;a&quot;).ToString();
        }
    }

And here is the GetQueryStringValue method:

    private static string GetQueryStringValue(string key)
    {
        return HttpContext.Current.Request.QueryString.Get(key);
    }

And the decrypt method looks like:

    public static string Decrypt(string cipherText, string password)
    {

        **// THE ERROR IS THROWN HERE!!**
        byte[] cipherBytes = Convert.FromBase64String(cipherText);

Can this error be remedied with a code fix or must I store ViewState in the database?

Invalid length for a Base-64 char array

Do you need to dispose of objects and set them to null, or will the garbage collector clean them up when they go out of scope?

Do you need to dispose of objects and set them to null?

I&#39;ve been trying to create a controller in my project for delivering what could turn out to be quite complex reports. As a result they can take a relatively long time and a progress bar would certainly help users to know that things are progressing. The report will be kicked off via an AJAX request, with the idea being that periodic JSON requests will get the status and update the progress bar.

I&#39;ve been experimenting with the AsyncController as that seems to be a nice way of running long processes without tying up resources, but it doesn&#39;t appear to give me any way of checking on the progress (and seems to block further JSON requests and I haven&#39;t discovered why yet). After that I&#39;ve tried resorting to storing progress in a static variable on the controller and reading the status from that - but to be honest that all seems a bit hacky!

All suggestions gratefully accepted!

Need an ASP.NET MVC long running process with user feedback

What&#39;s the reason why Java doesn&#39;t allow us to do

    private T[] elements = new T[initialCapacity];

I could understand .NET didn&#39;t allow us to do that, as in .NET you have value types that at run-time can have different sizes, but in Java all kinds of T will be object references, thus having the same size (correct me if I&#39;m wrong).

What is the reason?

What&#39;s the reason I can&#39;t create generic array types in Java?

Will a static constructor on a generic class be run for every type you pass into the generic parameter such as this:

     class SomeGenericClass&lt;T&gt;
     {
          static List&lt;T&gt; _someList;
          static SomeGenericClass()
          {
              _someList = new List&lt;T&gt;();
          }
     }

Are there any draw backs to using this approach?

C# Generic Static Constructor

I am trying to create a generic extension that uses &#39;TryParse&#39; to check if a string is a given type:

    public static bool Is&lt;T&gt;(this string input)
    {
        T notUsed;
        return T.TryParse(input, out notUsed);
    }

this won&#39;t compile as it cannot resolve symbol &#39;TryParse&#39;

As I understand, &#39;TryParse&#39; is not part of any interface.

Is this possible to do at all?

**Update:**

Using the answers below I have come up with:

    public static bool Is&lt;T&gt;(this string input)
    {
        try
        {
            TypeDescriptor.GetConverter(typeof(T)).ConvertFromString(input);
        }
        catch
        {
            return false;
        }

        return true;
    }

It works quite well but I think using exceptions in that way doesn&#39;t feel right to me.

**Update2:**

Modified to pass type rather than use generics:

    public static bool Is(this string input, Type targetType)
    {
        try
        {
            TypeDescriptor.GetConverter(targetType).ConvertFromString(input);
            return true;
        }
        catch
        {
            return false;
        }
    }

Generic TryParse

I would like to differentiate between following cases:

 1. A plain value type (e.g. `int`)
 2. A nullable value type (e.g. `int?`)
 3. A reference type (e.g. `string`) - optionally, I would not care if this mapped to (1) or (2) above

I have come up with the following code, which works fine for cases (1) and (2):

    static void Foo&lt;T&gt;(T a) where T : struct { } // 1

    static void Foo&lt;T&gt;(T? a) where T : struct { } // 2

However, if I try to detect case (3) like this, it does not compile:

    static void Foo&lt;T&gt;(T a) where T : class { } // 3

The error message is _Type &#39;X&#39; already defines a member called &#39;Foo&#39; with the same parameter types_. Well, somehow I cannot make a difference between `where T : struct` and `where T : class`.

If I remove the third function (3), the following code does not compile either:

    int x = 1;
    int? y = 2;
    string z = &quot;a&quot;;

    Foo (x); // OK, calls (1)
    Foo (y); // OK, calls (2)
    Foo (z); // error: the type &#39;string&#39; must be a non-nullable value type ...

How can I get `Foo(z)` to compile, mapping it to one of the above functions (or a third one with another constraint, which I have not thought of)?

Generic constraints, where T : struct and where T : class

This is a small snippet of code taken from some of the examples that accompany the Stanford Parser.  I&#39;ve been developing in Java for about 4 years, but have never had a very strong understanding of what this style of code is supposed to indicate.

    List&lt;? extends HasWord&gt; wordList = toke.tokenize();

I&#39;m not worried about the details of the code.  What I&#39;m confused about is what exactly the generic expression is supposed to convey, in English.

Can someone explain this to me?


What does the question mark in Java generics&#39; type parameter mean?

Say I have a base class TestBase where I define a virtual method TestMe()

    class TestBase
    {
        public virtual bool TestMe() {  }
    }

Now I inherit this class:

    class Test1 : TestBase
    {
        public override bool TestMe() {}
    }


Now, using Reflection, I need to find if the method TestMe has been overriden in child class - is it possible? 


What I need it for - I am writing a designer visualizer for type &quot;object&quot; to show the whole hierarchy of inheritance and also show which virtual methods were overridden at which level.

Detect if a method was overridden using Reflection (C#)

I realize that, generally speaking, there are performance implications of using reflection. (I myself am not a fan of reflection at all, actually; this is a purely academic question.)

Suppose there exists some class that looks like this:

    public class MyClass {
        public string GetName() {
            return &quot;My Name&quot;;
        }
    }

Bear with me here. I know that if I have an instance of `MyClass` called `x`, I can call `x.GetName()`. Furthermore, I could set a `Func&lt;string&gt;` variable to `x.GetName`.

Now here&#39;s my question. Let&#39;s say I *don&#39;t* know the above class is called `MyClass`; I&#39;ve got some object, `x`, but I have no idea what it is. I could check to see if that object has a `GetName` method by doing this:

    MethodInfo getName = x.GetType().GetMethod(&quot;GetName&quot;);

Suppose `getName` is not null. Then couldn&#39;t I furthermore check if `getName.ReturnType == typeof(string)` and `getName.GetParameters().Length == 0`, and at this point, wouldn&#39;t I be quite certain that the method represented by my `getName` object could *definitely* be cast to a `Func&lt;string&gt;`, somehow?

I realize there&#39;s a `MethodInfo.Invoke`, and I also realize I could always *create* a `Func&lt;string&gt;` like:

    Func&lt;string&gt; getNameFunc = () =&gt; getName.Invoke(x, null);

I guess what I&#39;m asking is if there&#39;s any way to go **from** a `MethodInfo` object **to** the actual method it represents, incurring the performance cost of reflection in the *process*, but *after* that point being able to call the method directly (via, e.g., a `Func&lt;string&gt;` or something similar) *without* a performance penalty.

What I&#39;m envisioning might look something like this:

    // obviously this would throw an exception if GetActualInstanceMethod returned
    // something that couldn&#39;t be cast to a Func&lt;string&gt;
    Func&lt;string&gt; getNameFunc = (Func&lt;string&gt;)getName.GetActualInstanceMethod(x);

(I realize that doesn&#39;t exist; I&#39;m wondering if there&#39;s anything *like* it.)


Can you get a Func&lt;T&gt; (or similar) from a MethodInfo object?

I have the class name stored in a property file. I know that the classes store will implement IDynamicLoad. How do I instantiate the class dynamically?

Right now I have

         Properties foo = new Properties();
        foo.load(new FileInputStream(new File(&quot;ClassName.properties&quot;)));
        String class_name = foo.getProperty(&quot;class&quot;,&quot;DefaultClass&quot;);
        //IDynamicLoad newClass = Class.forName(class_name).newInstance();


Does the newInstance only load compiled .class files? How do I load a Java Class that is not compiled?

How do I programmatically compile and instantiate a Java class?

I have an object (basically a VO) in Java and I don&#39;t know its type.  
I need to get values which are not null in that object. 

How can this be done?

How to get the fields in an Object via reflection?

While trying to learn [Unity][1], I keep seeing the following code for overriding `GetControllerInstance` in MVC:

    if(!typeof(IController).IsAssignableFrom(controllerType)) { ... }

this seems to me a pretty convoluted way of basically writing

    if(controllerType is IController) { ... }

I appreciate there are subtle differences between `is` and `IsAssignableFrom`, ie `IsAssignableFrom` doesn&#39;t include cast conversions, but I&#39;m struggling to understand the implication of this difference in practical scenarios.

When is it imporantant to choose `IsAssignableFrom` over `is`? What difference would it make in the `GetControllerExample`?

    if (!typeof(IController).IsAssignableFrom(controllerType))
          throw new ArgumentException(...);
    return _container.Resolve(controllerType) as IController;
                


  [1]: http://weblogs.asp.net/shijuvarghese/archive/2010/05/07/dependency-injection-in-asp-net-mvc-nerddinner-app-using-unity-2-0.aspx

Content Type	Original Author	Original Content on Stackoverflow
Question	DJPB	View Question on Stackoverflow
Solution 1 - C#	Lee	View Answer on Stackoverflow
Solution 2 - C#	SWeko	View Answer on Stackoverflow
Solution 3 - C#	vtortola	View Answer on Stackoverflow

How to convert string to any type

C# Problem Overview

C# Solutions

Solution 1 - C#

Solution 2 - C#

Solution 3 - C#

How can I undo a mysql statement that I just executed?

iPhone - dequeueReusableCellWithIdentifier usage

Attributions