How to access an object array as Hashvalue in C#

Question

Why does the following throws the compile error [] cannot be applied to object. (rough translation from german)?

Hashtable entrys = new Hashtable();
string keyPath = "HKEY_CURRENT_USER\\Software\\Test";
string entryName = "testName";

entrys.Add(entryName, new object[]{256, RegistryValueKind.DWord}); // seems to work

foreach(DictionaryEntry entry in entrys)
{
    Registry.SetValue(keyPath,
                      (string)entry.Key,
                      entry.Value[0],   // error here
                      entry.Value[1]);  // and here
}

I expected entry.Value to be an array of objects but apparently the compiler thinks it's just an object. What is wrong here?

check this for correct usage of Registry.SetValue -msdn.microsoft.com/en-us/library/3dwk5axy(v=vs.110).aspx — Nikita Shrivastava
– Nikita Shrivastava, Commented Oct 7, 2015 at 7:01
Use Dictionary<string, object[]> instead of Hashtable. Hashtable isn't strongly typed — Sriram Sakthivel
– Sriram Sakthivel, Commented Oct 7, 2015 at 7:11

Gagan Jaura · Accepted Answer · 2015-10-07 07:22:37Z

2

The error is coming because DictionaryEntry does not have an array as a property for Value. Below is the structure of DictionaryEntry. You must use entry.Value instead of entry.Value[0]

    // Summary:
    // Defines a dictionary key/value pair that can be set or retrieved.
    [Serializable]
    [ComVisible(true)]
    public struct DictionaryEntry
    {            
        public DictionaryEntry(object key, object value);

        // Summary:
        //     Gets or sets the key in the key/value pair.
        //
        // Returns:
        //     The key in the key/value pair.
        public object Key { get; set; }
        //
        // Summary:
        //     Gets or sets the value in the key/value pair.
        //
        // Returns:
        //     The value in the key/value pair.
        public object Value { get; set; }
    }

EDIT

To make it work you have to cast it. Use following code

Registry.SetValue(keyPath,
                  (string)entry.Key,
                  ((object[])(entry.Value))[0]);

edited Oct 7, 2015 at 7:22

answered Oct 7, 2015 at 7:08

Gagan Jaura

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3 Comments

SimonH Over a year ago

So that means entrys.Add(entryName, new object[]{256, RegistryValueKind.DWord}); is actually not valid because a DictionaryEntry cannot hold an array as value? I thought entry.Value returns my object-array which I could acces via []-operator? Should I use an ArrayList instead or what could I do?

Gagan Jaura Over a year ago

I have edited my answer. See the EDIT portion. Its working.

MrFox Over a year ago

entry.Value is an object array, the dictionary is just not aware of that. That's why casting works. You might wanna use a System.Collection.Generic.HashSet<object[]> since it has a generic implementation (allows you to choose a type for the items).

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