Hi, I'm trying to make some sort of database with a json file. I read in the Docs that with "DynamicConfigFile["KEY1"]["KEY2"]["KEY3"]" we can go throught the nested keys of the save files but when I try to do that I get "Cannot apply indexing with [] to an expression of type 'object'" how can I fix it ?

I'm not sure were you saw that, but that doesn't appear to be right. 

An example of subdirectory nesting is below, though not sure that is what you want:

DynamicConfigFile dataFile = Interface.Oxide.DataFileSystem.GetFile("PluginName/SubPath");
Interface.Oxide.DataFileSystem.SaveDatafile("PluginName/SubPath");

if (dataFile["EpicCategory"]["EpicString"] != null)
{
    Puts(dataFile["EpicCategory"]["EpicString"]); // Outputs: EpicValue
}

There is an error in the actual doc... To get a nested key you have to put a "," between the args to go throught it like that

Puts(dataFile["EpicCategory", "EpicString"]);

and not like the doc says. (So the doc is wrong)

That would be usefull to correct that ;)

That usage would actually be valid depending on what the dataFile variable actually is, just as if you put a comma there; it all depends on what the variable is defined as.

Idk I just do that to get the actual dataFile

private static DataFileSystem dataFile = Interface.Oxide.DataFileSystem;
private DynamicConfigFile ArenasData = dataFile.GetDatafile("Arenas");​

//So I could normally do that

string MyVar = (string)ArenasData["KeyToString1"]["KeyToString2"]; //But throws the error

Here's an example of what you are looking for I believe:

            DynamicConfigFile dataFile = Interface.Oxide.DataFileSystem.GetDatafile("PluginName");
            Dictionary<string, string> allData = dataFile["EpicCategory"] as Dictionary<string, string>;
            if (allData["EpicString"]["EpicString"] != null)
            {
                Puts(allData["EpicString"]["EpicString"]); // Outputs: EpicValue
            }​

How ok you made it into a dictionary !What if I had an other key ? Like a third one ? I have to create a dictionary onto a dictionary and instantiate a new dictionary by adding the firstkey like that ?

DynamicConfigFile dataFile = Interface.Oxide.DataFileSystem.GetDatafile("PluginName");
Dictionary> allData = dataFile["EpicCategory"] as Dictionary>;
if(!allData.Containskey("EpicCategory"))
{
        allData.Add("EpicCategory", new Dictionary());
}
if (allData["EpicString"]["EpicString"]["EpicString"] != null)
{
        Puts(allData["EpicString"]["EpicString"]["EpicString"]); // Outputs: EpicValue
}​​

Yes.

var depthThree = new Dictionary<string, Dictionary<string, Dictionary<string, string>>>​