Remove duplicate key from dictionary using linq in C#

Question

I have tried below code to remove duplicate key from dictionary before adding it.

Sample code:

string conString = "Host = local;UserName = UID; Password = PWD;Host =localhost";
        var sp = conString.Split(';');
        Dictionary<string, string> keyValue = new Dictionary<string, string>();
        foreach (var k in sp)
        {
            if (k.Contains('='))
            {
                var conSP = k.Split(new char[] { '=' }, 2);
                if (keyValue.All(i =>
                 i.Key != conSP[0]))
                    keyValue.Add(conSP[0], conSP[1]);
            }
        }

Sample Result:

KeyValue[0].Key = Host, KeyValue[0].Value = local
KeyValue[1].Key = username, KeyValue[1].Value = UID
KeyValue[2].Key = Password, KeyValue[2].Value = PWD

But I need same result using linq. So I tried below code with linq to get output.

var keyValue = conString.Split(';')
                               .Where(kvp => kvp.Contains('='))
                               .Select(kvp => kvp.Split(new char[] { '=' }, 2))
                               .ToDictionary(kvp => kvp[0].Trim(),kvp => kvp[1].Trim(),StringComparer.InvariantCultureIgnoreCase); 

But in this code I got the below exception.

"An item with the same key has already been added"

Can anyone suggest me how to resolve this?

Thanks in advance.

Answer 1

You could try this LINQ query:

var d = sp.Select(x => x.Split('='))
          .GroupBy(x => x[0])
          .Select(x => x.First())
          .ToDictionary(x => x[0], x=> x[1]);

Result:

[Host ,  local]
[UserName ,  UID]
[Password ,  PWD]

Answer 2

As @Sedat Kapanoglu described; you shouldn't add duplicate item. You should check it before adding. So, to remove duplicates, you can perform it like this;

        var keyValue = conString.Split(';')
            .Where(kvp => kvp.Contains('='))
            .Select(kvp => kvp.Split(new char[] { '=' }, 2))
            .GroupBy(kvp => kvp[0])
            .Select(kvp => kvp.FirstOrDefault())
            .ToDictionary(kvp => kvp[0].Trim(), kvp => kvp[1].Trim(), StringComparer.InvariantCultureIgnoreCase);

Answer 3

Connection String Builder is more apropriate for parsing connection strings, but it keeps the last value:

new System.Data.Odbc.OdbcConnectionStringBuilder(
                              "Host = local;UserName = UID; Password = PWD;Host =localhost")

results in:

Key         Value
host        localhost
username    UID
password    PWD