.NET应用和以太坊智能合约的桥梁

作者:jcmp      发布时间:2021-04-19      浏览量:0
Nethereum基本上是目前唯一可用的

Nethereum基本上是目前唯一可用的.NET平台下的web3.js移植包。在这个教程中,我们将首先编写并部署一个简单的智能合约,然后创建一个简单的.NET应用,并使用Nethereum来访问以太坊上的智能合约。Nethereum是通过以太坊节点旳标准RPC接口访问智能合约,因此使用Nethereum可以对接所有的以太坊节点实现,例如geth或parity。

一、智能合约开发与部署

首先安装开发用以太坊节点软件Ganache:

~$ npm install -g ganache-cli

然后安装以太坊开发框架Truffle:

~$ npm install -g truffle

现在创建一个项目目录,进入该目录,并执行 truffle init 进行初始化:

~$ mkdir demo && cd hubwiz~/hubwiz$ truffle init。

truffle会创建一些新的文件夹:contract、test、migration等。在contract文件夹中,创建一个新的合约文件Vote.sol:

~/hubwiz/contracts$ touch Vote.sol。

按如下内容编辑Vote.sol,这个合约只是简单地跟踪两个候选人的得票数,它使用交易发起账户作为投票人,并且每个账户只能投一票:

pragma solidity ^0.4.16; contract Vote { uint public candidate1; uint public candidate2; mapping (address => bool) public voted; function castVote(uint candidate) public { require(!voted[msg.sender] && (candidate == 1 || candidate == 2)); if(candidate == 1){ candidate1++; }else{ candidate2++; } voted[msg.sender] = true; } }

接下来在migration文件夹创建一个新的js文件2_vote.js,内容如下:

var vote = artifacts.require("Vote"); module.exports = function(deployer) { // deployment steps deployer.deploy(vote); };

然后打开项目文件夹下的truffle.js,用以下内容替换:

module.exports = { networks: { ganache: { host: "127.0.0.1", port: 7545, network_id: "*" // Match any network id } } };

现在打开一个终端,启动ganache:

~$ ganache-cli

然后打开另一个终端,用truffle部署合约:

~/hubwiz$ truffle deploy --reset --network ganache。

你会看到终端输出类似下面的合约地址,拷贝下来,后面还要用到:

Vote: 0xe4e47451aad6c89a6d9e4ad104a7b77ffe1d3b36。

二、.Net应用开发与智能合约访问

然后按如下内容修改program.cs:

using System; using System.Numerics; using System.Threading.Tasks; using Nethereum.Contracts; using Nethereum.Hex.HexTypes; using Nethereum.Web3; namespace console { class Program { static void Main(string[] args) { //The URL endpoint for the blockchain network. string url = "HTTP://localhost:7545"; //The contract address:合约部署的地址 string address = "0x345cA3e014Aaf5dcA488057592ee47305D9B3e10"; //The ABI for the contract. string ABI = @"[{'constant':true,'inputs':[],'name':'candidate1','outputs':[{'name':'','type':'uint256'}],'payable':false,'stateMutability':'view','type':'function'},{'constant':false,'inputs':[{'name':'candidate','type':'uint256'}],'name':'castVote','outputs':[],'payable':false,'stateMutability':'nonpayable','type':'function'},{'constant':true,'inputs':[],'name':'candidate2','outputs':[{'name':'','type':'uint256'}],'payable':false,'stateMutability':'view','type':'function'},{'constant':true,'inputs':[{'name':'','type':'address'}],'name':'voted','outputs':[{'name':'','type':'bool'}],'payable':false,'stateMutability':'view','type':'function'}]"; //Creates the connecto to the network and gets an instance of the contract. Web3 web3 = new Web3(url); Contract voteContract = web3.Eth.GetContract(ABI, address); //Reads the vote count for Candidate 1 and Candidate 2 Task candidate1Function = voteContract.GetFunction("candidate1").CallAsync(); candidate1Function.Wait(); int candidate1 = (int)candidate1Function.Result; Task candidate2Function = voteContract.GetFunction("candidate2").CallAsync(); candidate2Function.Wait(); int candidate2 = (int)candidate2Function.Result; Console.WriteLine("Candidate 1 votes: {0}", candidate1); Console.WriteLine("Candidate 2 votes: {0}", candidate2); //Prompts for the account address. Console.Write("Enter the address of your account: "); string accountAddress = Console.ReadLine(); //Prompts for the users vote. int vote = 0; Console.Write("Press 1 to vote for candidate 1, Press 2 to vote for candidate 2: "); Int32.TryParse(Convert.ToChar(Console.Read()).ToString(), out vote); Console.WriteLine("You pressed {0}", vote); //Executes the vote on the contract. try{ HexBigInteger gas = new HexBigInteger(new BigInteger(400000)); HexBigInteger value = new HexBigInteger(new BigInteger(0)); Task castVoteFunction = voteContract.GetFunction("castVote").SendTransactionAsync(accountAddress, gas, value, vote); castVoteFunction.Wait(); Console.WriteLine("Vote Cast!"); }catch(Exception e){ Console.WriteLine("Error: {0}", e.Message); } } } }

别忘了用你自己部署的合约地址修改上面代码中的合约地址。现在运行应用,就可以投票了!

汇智网翻译,转载请标明出处。原文链接: Interfacing .NET and Ethereum Blockchain Smart Contracts with Nethereum。