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POTrouble deep-copying a 'List<T>' C#
 

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  1. POTrouble deep-copying a 'List<T>' C#
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    <p>I am having trouble with deep-copying a list.</p> <p>My main window, called <code>Form1</code>, has an instance of <code>System.Collections.Generic.List&lt;T&gt;</code> and I wish to provide the ability to edit this list through a separate <code>SettingsForm</code> which has an OK- and a Cancel-button. If the user presses "OK" then the changes to the list shall take effect but if the user presses "Cancel" then (naturally) all changes must be dismissed. To achieve this <code>SettingsForm</code> is meant to make a deep copy of the list, make any changes the user requests to the copied list, and then - if the user presses "OK - hand the edited copy back to <code>Form1</code> to replace the original.</p> <p>To make the deep copy I am using the <code>MemoryStream</code>-<code>BinaryFormatter</code> solution suggested <a href="https://stackoverflow.com/questions/129389/how-do-you-do-a-deep-copy-an-object-in-net-c-specifically">here</a> and my problem is that when I call up <code>SettingsForm</code> a second time I get an exception from my deep-copy function stating that <code>null</code> is not serializable. It is as if I had passed <code>null</code> to the deep-copy function but I have taken care not to.</p> <p>Well, if you've read this far I'm guessing that you would like to see some code, so here we go; first the relevant parts of <code>Form1</code>:</p> <pre><code>public partial class Form1 : Form { ... private List&lt;ScriptListEntry&gt; scriptList; ... public Form1() { InitializeComponent(); ... // Create an empty script list scriptList = new List&lt;ScriptListEntry&gt;(); ... } ... private void toolStripButton2_Click(object sender, EventArgs e) { /* Will display 'SettingsForm' to allow the user to change the program * settings. */ ... SettingsForm sform = new SettingsForm(); ... sform.setScriptList(scriptList); sform.ShowDialog(); } </code></pre> <p><br> <br> Then <code>SettingsForm</code></p> <pre><code>public partial class SettingsForm : Form { ... private List&lt;ScriptListEntry&gt; scriptList; private List&lt;ScriptListEntry&gt; scriptListWorkingCopy; public SettingsForm() { InitializeComponent(); scriptList = null; scriptListWorkingCopy = null; ... } public void setScriptList(List&lt;ScriptListEntry&gt; scriptList_) { // Keep a reference to the original list scriptList = scriptList_; if (null != scriptList_) { if (0 != scriptList_.Count) { /* Make a working copy because settings made in 'SettingsForm' must * not be committed until OK-button is clicked. 'DeepCopy' does not * work if object to be copied is 'null' or the list is empty. */ scriptListWorkingCopy = DeepCopy&lt;List&lt;ScriptListEntry&gt;&gt;.deepCopy(scriptList_); ... } } else ... } ... // OK-button private void button1_Click(object sender, EventArgs e) { ... // Update the script list if (null != scriptList) { scriptList.Clear(); scriptList.AddRange(scriptListWorkingCopy); } else ... } </code></pre> <p><br> <br> And finally the deep-copy-machine, line 11 below throws the exception</p> <pre><code>public static class DeepCopy&lt;T&gt; { /* Used for deep copying anything. * Class 'T' must have [SerializableAttribute] */ public static T deepCopy(object objectToCopy) { using (MemoryStream memoryStream = new MemoryStream()) { BinaryFormatter binaryFormatter = new BinaryFormatter(); binaryFormatter.Serialize(memoryStream, objectToCopy); // &lt;&lt; Exception thrower memoryStream.Seek(0, SeekOrigin.Begin); return (T)binaryFormatter.Deserialize(memoryStream); } } } </code></pre> <p>Creating the list for the first time works just fine (I've verified its contents) but when I try to bring up 'SettingsForm' a second time the exception occurs. The exception is 'System.Runtime.Serialization.SerializationException' - "PublicKeyToken=null' is not marked as serializable"</p> <p>Thank you for reading!</p>
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    1. USCommunity
    1. USjokki
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      1. POTrouble deep-copying a 'List<T>' C#
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    1. COIs ScriptListEntry serializable? Have you tried testing serializing a single instance of it?
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      1. POTrouble deep-copying a 'List<T>' C#
      1. USLilith River
    2. COHave you tried stepping through to find any differences in what's being passed into `deepCopy`?
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      1. POTrouble deep-copying a 'List<T>' C#
      1. USWill Vousden
    3. COI had missed to make 'ScriptListEntry' serializable - see below. Thank you for your comments!
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      1. POTrouble deep-copying a 'List<T>' C#
      1. USjokki
 

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