IDictionary to string

Question

I have created an IDictionary extension to write IDictionary Exception.Data values to a string.

The extension code:

public static class DictionaryExtension
{
    public static string ToString<TKey, TValue>(this IDictionary<TKey, TValue> source, string keyValueSeparator, string sequenceSeparator)
    {
        if (source == null)
            throw new ArgumentException("Parameter source can not be null.");

        return source.Aggregate(new StringBuilder(), (sb, x) => sb.Append(x.Key + keyValueSeparator + x.Value + sequenceSeparator), sb => sb.ToString(0, sb.Length - 1));           
    }
}

When I use this extension on Exception.Data.ToString("=", "|") I get error

The type arguments cannot be inferred from the usage.

Any idea how to solve this?

The problem is probably related to the fact that `Exception.Data` is an `IDictionary`, not an `IDictionary<,>`. I'm surprised it calls the extension method at all. — Thom Smith, Aug 30 '12 at 12:48
@ThomSmith: It doesn't call the extension method. The **compiler error** happens on the line `Exception.Data.ToString("=", "|")` — Daniel Hilgarth, Aug 30 '12 at 12:50
Check this [Convert object htmlAttributes to string][1] [1]: http://stackoverflow.com/questions/6434865/passing-an-object-to-html-attributes — ayette, May 24 '14 at 00:52

Daniel Hilgarth · Accepted Answer · 2012-08-30T12:52:00.170

7

Exception.Data is of type IDictionary, not IDictionary<TKey, TValue>.

You need to change your extension method to this:

public static string ToString(this IDictionary source, string keyValueSeparator,
                                                       string sequenceSeparator) 
{ 
    if (source == null) 
        throw new ArgumentException("Parameter source can not be null."); 

    return source.Cast<DictionaryEntry>()
                 .Aggregate(new StringBuilder(),
                            (sb, x) => sb.Append(x.Key + keyValueSeparator + x.Value
                                                  + sequenceSeparator),
                            sb => sb.ToString(0, sb.Length - 1));            
}

edited Aug 30 '12 at 12:52

answered Aug 30 '12 at 12:44

Daniel Hilgarth

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Then I get the same exception on source.Aggregate – Tomas Aug 30 '12 at 12:49
@Tomas: That's a **compiler error** you are getting, not an exception. Exceptions happen at runtime. Anyway, please see update. The important part is the `Cast()`. – Daniel Hilgarth Aug 30 '12 at 12:52

score 0 · Answer 2 · answered Aug 30 '12 at 13:16

The exception is pointing that you are missing a cast. I copied your code in a test project but I was unable to reproduce your error. Try using x.Key.ToString() and x.Value.ToString(). The only thing I found is an error raised when Dictionary is empty: sb.ToString(0, sb.Length - 1) when lenght is zero is not working

IDictionary to string

2 Answers2

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