currently I'm resorting to

FunctionApp lastApp = null!;

            foreach (var app in apps)
            {
                ComponentResourceOptions options = lastApp == null ? null! : new ComponentResourceOptions {
                    DependsOn = {
                        lastApp
                    }
                };

                var cosmosDbRoles = new CosmosDbRoles($"{StackConstants.ApplicationName.ToLower()}-{app.Key}-cosmosdbroles",
                    new CosmosDbRoleArgs()
                    {
                        ResourceGroupName = globalResourceGroup.Name,
                        FunctionIdentity = app.Value.AppIdentity,
                        CosmosDatabaseAccountName = cosmos.CosmosDatabaseAccountName,
                        CosmosDatabaseAccountId = cosmos.CosmosDatabaseAccountId
                    }, options);
                 lastApp = app.Value;
            }

have you tried a

reduce

(or whatever the equivalent is in .Net -

Aggregate

?)

the issue is passing the dependson down to the resources in order

actually after looking a bit more at your code i think a simple 

map

 would work (this is pseudocode since I don't know .Net languages)

const cosmosStuff = apps.map((app, index) => {
    return {
        componentResourceOptions: index == 0 ? null! : new ComponentResourceOptions { DependsOn = { apps[index-1].Value }};
        cosmosDbRoles: new CosmosDbRoles($"{StackConstants.ApplicationName.ToLower()}-{app.Key}-cosmosdbroles",
            new CosmosDbRoleArgs() {
                ResourceGroupName = globalResourceGroup.Name,
                FunctionIdentity = app.Value.AppIdentity,
                CosmosDatabaseAccountName = cosmos.CosmosDatabaseAccountName,
                CosmosDatabaseAccountId = cosmos.CosmosDatabaseAccountId
            },
            options
        );
    }
})

The only difference is the index, which is admittedly marginally nicer, but still, that doesn't feel like the best option.

it also removes mutability and allows access to the 

new

 resources in the returned array. there might be a better way if given more specifics about the problem you're trying to solve, but without that this will be the simplest it gets

You could do LINQ Aggregate like @steep-toddler-94095 originally suggested. You would set the starting value to null and return the current item in the sequence each time. Then you could do it in a function without the for loop or the indexing. But I also don't know why this makes you feel dirty. It is what it is.

I suppose its because I want a nice factory style apply method... l have a go at a wrapper though.