Reactive-Extensions/LevelDB

// Open a connection to a new DB and create if not found
var options = new Options { CreateIfMissing = true };
var db = new DB(options, @"C:\temp\tempdb");

// Close the connection
db.Close();

var options = new Options { CreateIfMissing = true };
using (var db = new DB(options, @"C:\temp\tempdb")) 
{
    // Use leveldb
}

const string key = "New York";

// Put in the key value
keyValue.Put(key, "blue");

// Print out the value
var keyValue = db.Get(key);
Console.WriteLine(keyValue); 

// Delete the key
db.Delete(key);

var options = new Options { CreateIfMissing = true };
using (var db = new DB(options, path))
{
    db.Put("NA", "Na");

    using(var batch = new WriteBatch())
    {
        batch.Delete("NA")
             .Put("Tampa", "Green")
             .Put("London", "red")
             .Put("New York", "blue");
        db.Write(batch);
    }
}

// Synchronously write
var writeOptions = new WriteOptions { Sync = true };
db.Put("New York", "blue");

var options = new Options { CreateIfMissing = true };
using (var db = new DB(options, path))
{
	db.Put("New York", "blue");

	// Create a batch to set key2 and delete key1
	using (var batch = new WriteBatch())
	{
		var keyValue = db.Get("New York");
		batch.Put("Tampa", keyValue);
		batch.Delete("New York");
		
		// Write the batch
		var writeOptions = new WriteOptions { Sync = true; }
		db.Write(batch, writeOptions);
	}
}

var keys = 
    from kv in db as IEnumerable<KeyValuePair<string, string>>
    select kv.Key;

foreach (var key in keys) 
{
	Console.WriteLine("Key: {0}", key);
}

// Create new iterator
using (var iterator = db.CreateIterator())
{
	// Iterate to print the keys as strings
	for (it.SeekToFirst(); it.IsValid(); it.Next()) 
	{
	    Console.WriteLine("Key as string: {0}", it.KeyAsString());
	}
}

// Create new iterator
using (var iterator = db.CreateIterator())
{
	// Iterate in reverse to print the values as strings
	for (it.SeekToLast(); it.IsValid(); it.Prev()) 
	{
	    Console.WriteLine("Value as string: {0}", it.ValueAsString());
	}
}

var options = new Options { CreateIfMissing = true }
using (var db = new Db(options, path))
{
    db.Put("Tampa", "green");
    db.Put("London", "red");
    db.Delete("New York");

	using (var snapshot = db.CreateSnapshot()) 
	{
		var readOptions = new ReadOptions {Snapshot = snapShot};

		db.Put("New York", "blue");

		// Will return null as the snapshot created before
		// the updates happened
		Console.WriteLine(db.Get("New York", readOptions)); 
	}
}

var options = new Options { CreateIfMissing = true };
options.Comparator = Comparator.Create(
    "integers mod 2",
    (xs, ys) => LexicographicalCompare(((NativeArray<int>) xs).Select(x => x % 2),
                                       ((NativeArray<int>) ys).Select(y => y % 2)));

using (var db = new Db(options, path))
{
    db.Put(1, new[] { 1, 2, 3 }, new WriteOptions());
    Console.WriteLine("put 1, [1,2,3]");

    var key = NativeArray.FromArray(new int[] { 3 });
    using (var xs = db.GetRaw<int>(key))
    {
		// Prints 1 2 3
        Console.WriteLine("get {0} => [{1}]", key[0], string.Join(",", xs));
    }
}

private int LexicographicalCompare<T>(IEnumerable<T> xs, IEnumerable<T> ys)
{
    var comparator = System.Collections.Generic.Comparer<T>.Default;

    using(var xe = xs.GetEnumerator())
    using(var ye = ys.GetEnumerator())
    {
        for(;;)
        {
            var xh = xe.MoveNext();
            var yh = ye.MoveNext();
            if (xh != yh)
                return yh ? -1 : 1;
            if (!xh)
                return 0;

            // more elements
            int diff = comparator.Compare(xe.Current, ye.Current);
            if (diff != 0)
                return diff;
        }
    }
}