C# can be used for blockchain development, particularly in the context of smart contract development for blockchain platforms like Ethereum. In this example, we'll introduce the basics of creating a simple smart contract using C# with the Nethereum library.

Sample C# Code for Smart Contract

Here's a basic example of C# code for a simple smart contract:

using Nethereum.Web3;
using Nethereum.ABI.FunctionEncoding.Attributes;
using System;
using System.Threading.Tasks;
[Function(`getValue`, `uint256`)]
public class GetValueFunction : FunctionMessage { }
[Function(`setValue`, `bool`)]
public class SetValueFunction : FunctionMessage
{
    [Parameter(`uint256`, `value`, 1)]
    public int Value { get; set; }
}
class Program
{
    static async Task Main()
    {
        var web3 = new Web3(`https://mainnet.infura.io/v3/YOUR_INFURA_PROJECT_ID`);
        var contractAddress = `0xYourSmartContractAddress`;
        var contract = new Contract(web3, `YourSmartContractAbi`, contractAddress);
        var getValueFunction = new GetValueFunction();
        var result = await contract.QueryDeserializingToObjectAsync<int>(getValueFunction);
        Console.WriteLine(`Current Value: ` + result);
        var setValueFunction = new SetValueFunction();
        setValueFunction.Value = 42;
        var transactionHash = await contract.SendTransactionAsync(setValueFunction);
        Console.WriteLine(`Transaction Hash: ` + transactionHash);
    }
}

This code provides a basic example of a C# program that interacts with an Ethereum smart contract using the Nethereum library. In a real application, you would work with more complex contracts, manage private keys securely, and implement additional features.

Important: Replace `'YOUR_INFURA_PROJECT_ID'`, `'YourSmartContractAddress'`, and `'YourSmartContractAbi'` with your actual Infura project ID, smart contract address, and ABI.