Custom driver - Multiple databases

loicwolff

I'm writing a custom driver, is there a way to have the same functionality as the "Display in a treeview" one from LINQPad where multiple databases are displayed in the tree view and the connections dropdown list? Especially the part where selecting the server-name.database-name from the dropdown changes the context of the query?

JoeAlbahari

This is possible - you'll need to override these properties of DataContextDriver:

/// <summary>Returns whether the connection a parent (default false). Parent connections can't themselves be queried, but they
/// have children which are queryable. An example is a SQL Server connection with the 'Show all databases in treeview'
/// option enabled: the parent displays the server, and the children are the databases. If you override this to return true,
/// also override the GetChildren method.</summary>
public virtual bool IsParent (IConnectionInfo cxInfo) => false;

/// <summary>For connections for which IsParent returns true, this should be overridden to return the child connections.
/// To create a child connection, call CreateChild on cxInfo (this clones all the properties), then assign the Database property
/// on the child (or whichever properties you want to specialize).</summary>
public virtual IConnectionInfo[] GetChildren (IConnectionInfo cxInfo, bool isOnStartup) => null;

/// <summary>Optional - If you're implementing a connection hierarchy ("Show all databases in treeview"),
/// override this to return the child node text.</summary>
public virtual string GetChildNodeName (IConnectionInfo cxInfo) => cxInfo.DatabaseInfo.Database;

/// <summary>Optional - if you're implementing a connection hierarchy ("Show all databases in treeview"),
/// you can override this to let users query more than one connection at a time.</summary>
public virtual void MergeConnections (ConnectionMergeArgs args) { }

loicwolff

Thank you for your response. I did find those while spelunking a bit, but it seems the GetChildren method is not called even if IsParent returns true.

Adding this to the UniversalStaticDriver class of the demo project show that only IsParent is called.

        public override bool IsParent(IConnectionInfo cxInfo)
        {
            return true;
        }

        public override IConnectionInfo[] GetChildren(IConnectionInfo cxInfo, bool isOnStartup)
        {
            var child1 = cxInfo.CreateChild();
            var child2 = cxInfo.CreateChild ();

            return new[]
            {
                child1,
                child2,
            };
        }

JoeAlbahari

Right now, this feature is available only with dynamic drivers.