---
uid: module-building.templates-csharp.how-to-update-appsettings-json-files
description: "How to add or merge configuration entries into appsettings.json from a template or factory extension using the ApplyAppSetting extension method."
---
# How to Update `appsettings.json` Files

The `Intent.VisualStudio.Projects` module automatically generates the `appsettings.json` file for supported .NET project types.

## How to Update from a Template

To apply additional configuration to an `appsettings.json` file, use the `ApplyAppSetting` extension method within your Template. For example:

```csharp
public override void BeforeTemplateExecution()
{
    this.ApplyAppSetting(
        field: "CustomSectionName:SomeStringField",
        value: "Some Value");

    this.ApplyAppSetting(
        field: "OtherCustomSectionName",
        value: new
        {
            IntValue = 10,
            StrValue = "My String"
        });
}
```

> [!NOTE]
> This extension method requires `Intent.Modules.Common.CSharp` NuGet package to be installed in your module project.
>
> [!IMPORTANT]
> This can only be invoked after construction of the template, otherwise the template which responds to this event might not yet have been constructed.
> 
> Placing this method in the override of either the `AfterTemplateRegistration` or `BeforeTemplateExecution` methods will ensure it is called only after all other templates have been constructed.

In the example above, the `appsettings.json` file will include the following:

```json
{
    // ... other configuration...

    "CustomSectionName": {
        "SomeStringField": "Some Value"
    },
    "OtherCustomSectionName": {
        "IntValue": 10,
        "StrValue": "My String"
    }
}
```

## How to update from a Factory Extension

It is also possible to apply additional configuration to an `appsettings.json` file using a `Factory Extension` with the `EventDispatcher`. For example:

``` csharp
protected override void OnAfterTemplateRegistrations(IApplication application)
{
    base.OnAfterTemplateRegistrations(application);
    
     application.EventDispatcher.Publish(new AppSettingRegistrationRequest(
        key: "CustomSectionName:SomeStringField",
        value: "Some Value"));

    application.EventDispatcher.Publish(new AppSettingRegistrationRequest(
        key: "OtherCustomSectionName",
        value: new
        {
            IntValue = 10,
            StrValue = "My String"
        }));
}
```

> [!NOTE]
> When providing a complex value, you should pass in an anonymous C# object as demonstrated above. Passing a JSON formatted string is not supported and will result in the string being escaped and written as a single value in the `appsettings.json` file, rather than being parsed as a JSON object.

The resulting `appsettings.json` file will be the same as in the previous `Template` example:

```json
{
    // ... other configuration...

    "CustomSectionName": {
        "SomeStringField": "Some Value"
    },
    "OtherCustomSectionName": {
        "IntValue": 10,
        "StrValue": "My String"
    }
}
```

## Variable field names

To create `appsettings.json` entries with variable field names, or to update an existing section, you can use the following syntax:

``` csharp
this.ApplyAppSetting(
   field: "OtherCustomSectionName:AdditionalStringValue",
   value: "AdditionalStrValue");
```

Executing this method after the previous above example, your `appsettings.json` file will look like the following:

```json
{
    // ... other configuration...

    "CustomSectionName": {
        "SomeStringField": "Some Value"
    },
    "OtherCustomSectionName": {
        "IntValue": 10,
        "StrValue": "My String",
        "AdditionalStringValue" : "AdditionalStrValue"
    }
}
```

## Environment specific appsettings.json files

To enable Intent Architect to generate separate `appsettings.json` files for each environment, you must configure the `runtime environments` in the Codebase Structure / Visual Studio modeling experience.

See [Codebase Structure Designer](https://docs.intentarchitect.com/docs-md/application-development/modelling/codebase-structure-designer/codebase-structure-designer.md) for where to add `Runtime Environment` elements and how they affect generated files.

![Runtime environments](images/runtime-environments.png)

This configuration will generate three additional appsettings files, in addition to the base appsettings.json file.

![Appsettings generation](images/appsettings-generation.png)

When the `ApplySetting` method is called, the `runtime environment` can be supplied, which will result in the setting only being applied to the relevant appsettings file.

``` csharp
this.ApplyAppSetting(
   field: "ProductionOnlySetting",
   value: "ProductionValue",
   runtimeEnvironment: "prod");
```