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Code Generation Demo with Visual Studio Code

Prerequisites

Imagine your goal is to take the contract called SimpleStorage.sol from the Solidity documentation and call its functions from a C# project.

Overview

You will prepare a Solidity contract in Visual Studio Code (VS Code) and compile it. The compilation process will automatically generate some C# API classes. These classes can then be consumed in a VS Code or Visual Studio C# project:

Overview

The diagram above shows these steps:

  • Write Solidity smart contracts and compile them in VS Code.

  • Configure the Solidity plugin for VS Code to automatically generate C# API classes that provide access to the smart contracts. This configuration only needs done once.

  • Use VS Code or Visual Studio to write C# to call methods from the generated C# API classes.

Initial Setup

  1. Create a folder structure as shown below:

Start

  1. Open Visual Studio Code.

  2. Open extensions and install the Solidity extension here if it is not already installed.

  3. Using VS Code, open the folder Contracts that you just created in step 1 above. To begin with, VS Code shows you just an empty tree:

TreeEmpty

  1. If at any time, VS Code shows popups asking things like “Required assets to build and debug are missing from ‘SimpleStorage’. Add them?” say yes.

  2. Create a new file (ctrl+N).

  3. Paste the following solidity code into the file:

pragma solidity >=0.4.0 <0.7.0;

contract SimpleStorage {
    uint storedData;

    function set(uint x) public {
        storedData = x;
    }

    function get() public view returns (uint) {
        return storedData;
    }
}
  1. Save the file as SimpleStorage.sol in the Contracts folder. The contract code is from the Solidity documentation and you can see it is a very simple contract, containing just two functions, set() and get(). VS Code should show the newly saved file in the tree like this:

TreeSol

  1. Press F1 and choose option Solidity: Create 'nethereum-gen.settings' with default values at root. This creates the Nethereum settings file to control the API generation. If VS Code says "the marketplace has extensions that can help with .settings files" choose "Dont show again". Edit the settings file to look like this, then save it:
{
    "projectName": "EthereumSmartContracts",
    "namespace": "EthereumSmartContracts.Contracts",
    "lang": 0,
    "autoCodeGen": true,
    "projectPath": "../"
}

Compile Contract

You are now ready to compile the contract.

  1. In VS Code, select the SimpleStorage.sol file from the tree.
  2. Press F1 and choose option Solidity: Compile Current Solidity Contract. This compiles the Solidity contract and the C# API classes are automatically generated at the same time. You should see a message saying "Compilation completed successfully".
  3. The very first time you do step 2 above, you also need to upgrade the Nethereum NuGet version in the generated project. To do this, open a command prompt in folder \NethereumCodeGenDemo\EthereumSmartContracts and enter:
dotnet add package Nethereum.Web3

Review What You've Built

You can now review what you've built so far. In VS Code, open the top level solution folder \NethereumCodeGenDemo and you should see a tree like this:

VSCodeBrowse

The contract is now compiled and the C# API classes have been generated. The generated SimpleStorageService class contains some useful methods for interacting with the contract:

To do this Call this C# Method
Deploy contract DeployContractAndWaitForReceiptAsync()
Call function set() SetRequestAndWaitForReceiptAsync()
Call function get() GetQueryAsync()

Notice the C# method naming is different for the set() and get() function calls. This is because set() changes a value on the blockchain so it has be called using a transaction which costs Ether and can return a receipt. The get() function doesn't change any values on the blockchain so it is a simple query call. Queries are free, there are no transaction and no receipt.

You have now written a smart contract and generated a C# API for it. This C# API can now be used as desired.

Where to go from here

There are many more demos available over on the Nethereum Playground.