How to convert Dictionary to Dictionary in c#

Question

I have below code in C#

Dictionary<string, object> dObject = new Dictionary<string, object>();

I want to convert dObject to Dictionary<string, string>. How can I do this?

Rune Grimstad · Accepted Answer · 2011-02-09T08:44:25.577

125

Use the ToDictionary method:

Dictionary<string, string> dString = dObject.ToDictionary(k => k.Key, k => k.Value.ToString());

Here you reuse the key from the original dictionary and you convert the values to strings using the ToString method.

If your dictionary can contain null values you should add a null check before performing the ToString:

Dictionary<string, string> dString = dObject.ToDictionary(k => k.Key, k => k.Value == null ? "" : k.Value.ToString());

The reason this works is that the Dictionary<string, object> is actually an IEnumerable<KeyValuePair<string,object>>. The above code example iterates through the enumerable and builds a new dictionary using the ToDictionary method.

Edit:

In .Net 2.0 you cannot use the ToDictionary method, but you can achieve the same using a good old-fashioned foreach:

Dictionary<string, string> sd = new Dictionary<string, string>(); 
foreach (KeyValuePair<string, object> keyValuePair in dict)
{
  sd.Add(keyValuePair.Key, keyValuePair.Value.ToString());
}

Edit2:

If you are on .Net 2.0 and you can have null values in the dictionary the following should be safe:

Dictionary<string, string> sd = new Dictionary<string, string>(); 
foreach (KeyValuePair<string, object> keyValuePair in dict)
{
  sd.Add(keyValuePair.Key, keyValuePair.Value == null ? "" : keyValuePair.Value.ToString());
}

edited Feb 09 '11 at 08:44

answered Feb 09 '11 at 08:24

Rune Grimstad

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I am using .NET 2.0, is possible in it. I am not getting "ToDictionary" – Manoj Singh Feb 09 '11 at 08:26
@Rune: Will `k.Value.ToString()` return always the same as `(string)k.Value`? – Oscar Mederos Feb 09 '11 at 08:32
@Oscar: No. the (string)k.Value will fail if the value is a non-string object. The ToString() is safe for all non-null values. – Rune Grimstad Feb 09 '11 at 08:32
@Rune: Yes, I know that. Let's suppose all elements are strings. Will `ToString()` and `(string)` return the same? – Oscar Mederos Feb 09 '11 at 08:35
What if there is NULL values in the key in .NET 2.0 solution – Manoj Singh Feb 09 '11 at 08:35
@Oscar: Yes. If all values are strings then they will do the same. In that case I believe casting to a string will be slightly faster. – Rune Grimstad Feb 09 '11 at 08:37
@MKS: Good point. You would have to do the same null check here as in the Linq-version. – Rune Grimstad Feb 09 '11 at 08:41
1

Might I suggest using `Convert.ToString()` instead. So it will be a little easier to deal with `null` values. `Convert.ToString(keyValuePair.Value)` or `Convert.ToString(keyValuePair.Value) ?? String.Empty` – Jeff Mercado Feb 09 '11 at 08:46
@Jeff M: Yeah. Good point! Convert.ToString is nice since you don't have to do a null check then. Convert.ToString(keyValuePair.Value) will be enough since it returns an empty string for null values. – Rune Grimstad Feb 09 '11 at 08:51
@Rune: Actually it will return `null` in the case the argument is `null`. Which is why I did the coalescing there. ;) – Jeff Mercado Feb 09 '11 at 08:54
@Jeff: `Convert.ToString()` actually returns `String.Empty` when the provided `value` is `null`. – Jaroslav Jandek Feb 09 '11 at 09:05
@Jaroslav: Ah, I stand corrected. I was testing with the wrong overload. `Convert.ToString(string)` returns `null`. – Jeff Mercado Feb 09 '11 at 09:23
@Jeff. Yep, that one actually does nothing else than returning the provided `value`. – Jaroslav Jandek Feb 09 '11 at 09:28

Jaroslav Jandek · Answer 2 · 2011-02-09T08:56:32.657

9

.NET 3.5:

Dictionary<string, string> result = dObject.ToDictionary(kvp => kvp.Key, kvp => Convert.ToString(kvp.Value));

.NET 2.0:

Dictionary<string, string> result = new Dictionary<string, string>();
foreach (KeyValuePair<string, object> kvp in dObject) result.Add(kvp.Key, Convert.ToString(kvp.Value));

edited Feb 09 '11 at 08:56

answered Feb 09 '11 at 08:27

Jaroslav Jandek

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score 4 · Answer 3 · edited Nov 02 '15 at 11:59

4

Since you are using .net 2.0:

Dictionary<string, string> dString = new Dictionary<string, string>();

foreach (KeyValuePair<string, object> item in dObject)
{
    dString.Add(item.Key, item.Value.ToString());
    //here item.Value.ToString() is an example
    //you should convert your item to string according to the requirement
}

edited Nov 02 '15 at 11:59

Shimmy Weitzhandler

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answered Feb 09 '11 at 08:29

Cheng Chen

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What if there is NULL values in it? – Manoj Singh Feb 09 '11 at 08:32
3

@MKS: That's why I'm saying "convert your item to string according to the requirement", for example you can use `string.Empty` for null values, or the string "NULL" for null values...everything depends on the requirement. – Cheng Chen Feb 09 '11 at 08:35
Sometime there can be null values also in the key, please suggest how to convert it? – Manoj Singh Feb 09 '11 at 08:41

score 2 · Answer 4 · answered Feb 09 '11 at 08:25

2

How about:

Dictionary<string, string> newDictionary = dObject.ToDictionary(k => k.Key, k => (string) k.Value);

answered Feb 09 '11 at 08:25

Arcturus

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This will fail if the dictionary contains non-string values. You cannot convert an int to a string for instance. – Rune Grimstad Feb 09 '11 at 08:30
First of all I am using .NET 2.0, is possible in it. I am not getting "ToDictionary" method. – Manoj Singh Feb 09 '11 at 08:31
Well, I suppose if he wants to do it is because the dictionary contains `strings`, but anyway, that's valid. – Oscar Mederos Feb 09 '11 at 08:33
Yeah true.. But ToString does not always produce a nice string. It all depends on your Dictionary objects anyhow. :) – Arcturus Feb 09 '11 at 08:41
1

Since you are using .NET 2.0, foreach will be your bestest buddy! GL – Arcturus Feb 09 '11 at 08:43

score 1 · Answer 5 · answered Feb 09 '11 at 08:31

In .Net 2.0 probably your best friend is foreach loop:

Dictionary<string, object> dObject = new Dictionary<string, object>();
Dictionary<string, string> newObjects = new Dictionary<string, string>();

foreach (KeyValuePair<string, object> keyValuePair in dObject)
{
    newObjects.Add(keyValuePair.Key, keyValuePair.Value.ToString());
}

Y.Yanavichus · Answer 6 · 2011-02-09T08:45:19.460

1

Dictionary<string, string> dString = dObject.ToDictionary(kvp => kvp.Key, kvp => kvp.Value.ToString());

It's just idea. You can insert any verifications.

edited Feb 09 '11 at 08:45

answered Feb 09 '11 at 08:32

Y.Yanavichus

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How to convert Dictionary to Dictionary in c#

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