# Key-Value storage tutorial with C# and NetCasperSDK

This example shows how to use the NetCasperSDK to:
- Fund a new account with 2500 $CSPR tokens from the faucet
- Deploy the key-value storage contract example to the network
- Call the contract to put a new string
- Query the contract state to read the value of the string

We are using a local network in this example. Learn [here](https://docs.casperlabs.io/en/latest/dapp-dev-guide/setup-nctl.html) how to install your own local network.

### Get a new instance of the client
Prepare an instance of the client and a couple of keys that will be used during the example:

static string nodeAddress = "http://207.154.217.11:11101/rpc";
static NetCasperClient casperSdk = new NetCasperClient(nodeAddress);

static KeyPair faucetAcct = KeyPair.FromPem("/tmp/faucetact.pem");
static KeyPair account2 = KeyPair.FromPem("/tmp/myaccount2.pem");

### Send $CSPR from the faucet account to `account2`
Use the `StandardTransfer` template to create a deploy object that orders a transfer of 2500 $CSPR. Sign it and deploy it to the network.

Take the `deploy_hash` from the response and make a call to `GetDeploy` with a timeout of 120 seconds to obtain the result of the transfer (testnet usually needs a longer timeout).

public static async Task FundAccount()
{
  var deploy = DeployTemplates.StandardTransfer(
                faucetAcct,
                account2.PublicKey,
                2500000000000,
                1200,
                "casper-net-1");

  deploy.Sign(faucetAcct);
  
  var response = await casperSdk.PutDeploy(deploy);

  string deployHash = response.GetDeployHash();

  var tokenSource = new CancellationTokenSource(TimeSpan.FromSeconds(120));
  response = await casperSdk.GetDeploy(deployHash, tokenSource.Token);
  File.WriteAllText("res_FundAccount.json", response.Result.GetRawText());
}

### Deploy the Key-Value Storage contract

You may find more information on the key-value storage contract used in this example here: [Key-Value Storage Tutorial](https://docs.casperlabs.io/en/latest/dapp-dev-guide/tutorials/kv-storage-tutorial.html).

If you haven't done yet, clone the repository and build the contract following the instruction in the README file.

git clone https://github.com/casper-ecosystem/kv-storage-contract
cd kv-storage-contract
cat README

Now use the `ContractDeploy` template to prepare a deploy object, sign it and deploy it.

public static async Task DeployKVStorageContract()
{
  var wasmFile = "./kv-contract-example/contract.wasm";
  var wasmBytes = System.IO.File.ReadAllBytes(wasmFile);

  var deploy = DeployTemplates.ContractDeploy(wasmBytes, account2,
                300000000000, "casper-net-1", 1, 1800000);
  deploy.Sign(account2);

  var response = await casperSdk.PutDeploy(deploy);
  Console.WriteLine(response.Result.GetRawText());

  string deployHash = response.GetDeployHash();
  var tokenSource = new CancellationTokenSource(TimeSpan.FromSeconds(120));
  response = await casperSdk.GetDeploy(deployHash, tokenSource.Token);

  Console.WriteLine(response.Result.GetRawText());
  File.WriteAllText("res_DeployContract.json", response.Result.GetRawText());
}

The deployment of the contract has added to the account a couple of named keys. We can retrieve the account information to see them:

public async static Task GetAccountInfo()
{
  var response = await casperSdk.GetAccountInfo(account2.PublicKey);
  Console.WriteLine(response.Result.GetRawText());
  File.WriteAllText("res_GetAccountInfo.json", response.Result.GetRawText());
}

Which outputs a response like this:

{
  "api_version": "1.0.0",
  "stored_value": {
    "Account": {
      "account_hash": "account-hash-989ca079a5e446071866331468ab949483162588d57ec13ba6bb051f1e15f8b7",
      "named_keys": [
        {
          "name": "counter",
          "key": "hash-4941592b93d3c766e077d19f1609b52e955735bbbf6182fe6b235eb0665414aa"
        },
        {
          "name": "kvstorage_contract",
          "key": "hash-0aaab9926971ac1564d6057d269aff4b93e621c788e2cfc2e9fbe48fac345285"
        },
        {
          "name": "kvstorage_contract_hash",
          "key": "uref-eafede874c50f50841e589825d41a6ff9c2abe12434f52d9a85816379f1acefd-007"
        }
      ],
      "main_purse": "uref-ea6dd32086d7878460a042357c8332d2d19251bb21f5ad809fc048855e167e9b-007",
      "associated_keys": [
        {
          "account_hash": "account-hash-989ca079a5e446071866331468ab949483162588d57ec13ba6bb051f1e15f8b7",
          "weight": 1
        }
      ],
      "action_thresholds": {
        "deployment": 1,
        "key_management": 1
      }
    }
  },
  "merkle_proof": "010..."
}

### Write a key-value pair

Next step is to call one of the entry points in the contract to store a string value. Note how we include two session arguments, one for the name of the key, one for the value.

public async static Task PutString()
{
    var sessionArgs = new List<NamedArg>();

    sessionArgs.Add(new NamedArg("name", CLValue.String("WorkingOn")));
    sessionArgs.Add(new NamedArg("value", CLValue.String("Friendly Hackaton")));

    var deploy = DeployTemplates.ContractCall("kvstorage_contract",
         "store_string",
         sessionArgs,
         account2,
         30000000000,
         "casper-net-1");
         deploy.Sign(account2);

    var response = await casperSdk.PutDeploy(deploy);

    string deployHash = response.GetDeployHash();
    var tokenSource = new CancellationTokenSource(TimeSpan.FromSeconds(120));
    response = await casperSdk.GetDeploy(deployHash, tokenSource.Token);

    Console.WriteLine(response.Result.GetRawText());
    File.WriteAllText("res_PutString.json", response.Result.GetRawText());
}

### Read the stored value

Finally, let's read the value we just stored in the `WorkingOn` key. To do that we are going to retrieve first the hash of the contract using the `GetAccountInfo` method. Then, we'll query the state of the contract with the `QueryState` method:

public async static Task ReadStringValue()
{
  // Get the contract hash
  //
  var response = await casperSdk.GetAccountInfo(account2.PublicKey);
  var namedKeys = response.Result.GetProperty("stored_value").GetProperty("Account")
             .GetProperty("named_keys");
  
  string kvStorageHash = null;
  
  foreach (var nk in namedKeys.EnumerateArray())
  {
    if (nk.GetProperty("name").GetString().Equals("kvstorage_contract"))
    {
      kvStorageHash = nk.GetProperty("key").GetString();
      break;
    }
  }

  if (kvStorageHash == null)
    throw new Exception("Contract hash not found.");
               
  // now read the string querying for the WorkingOn key
  //
  response = await casperSdk.QueryState(kvStorageHash,
               new List<string>() {"WorkingOn"});

  Console.WriteLine(response.Result.GetRawText());
  File.WriteAllText("res_ReadString.json", response.Result.GetRawText());
}

### Full example code

`Program.cs`

using System;
using System.Collections.Generic;
using System.IO;
using System.Net.Http;
using System.Threading;
using System.Threading.Tasks;
using NetCasperSDK;
using NetCasperSDK.JsonRpc;
using NetCasperSDK.Types;
using NetCasperSDK.Utils;

namespace CasperMain
{
    public static class KeyValueStorageContract
    {
        static string nodeAddress = "http://207.154.217.11:11101/rpc";

        static KeyPair faucetAcct = KeyPair.FromPem("/tmp/faucetact.pem");
        static KeyPair account2 = KeyPair.FromPem("/tmp/myaccount2.pem");

        static NetCasperClient casperSdk;

        public static async Task FundAccount()
        {
            var deploy = DeployTemplates.StandardTransfer(
                faucetAcct,
                account2.PublicKey,
                25000000000000,
                1200,
                "casper-net-1");

            deploy.Sign(faucetAcct);

            var response = await casperSdk.PutDeploy(deploy);

            string deployHash = response.GetDeployHash();

            var tokenSource = new CancellationTokenSource(TimeSpan.FromSeconds(120));
            response = await casperSdk.GetDeploy(deployHash, tokenSource.Token);

            File.WriteAllText("res_FundAccount.json", response.Result.GetRawText());
        }

        public static async Task DeployKVStorageContract()
        {
            var wasmFile = "./kv-contract-example/contract.wasm";
            var wasmBytes = System.IO.File.ReadAllBytes(wasmFile);

            var deploy = DeployTemplates.ContractDeploy(wasmBytes, account2,
                300000000000, "casper-net-1", 1, 1800000);
            deploy.Sign(account2);

            var response = await casperSdk.PutDeploy(deploy);
            Console.WriteLine(response.Result.GetRawText());

            string deployHash = response.GetDeployHash();
            var tokenSource = new CancellationTokenSource(TimeSpan.FromSeconds(120));
            response = await casperSdk.GetDeploy(deployHash, tokenSource.Token);

            Console.WriteLine(response.Result.GetRawText());
            File.WriteAllText("res_DeployContract.json", response.Result.GetRawText());
        }

        public async static Task GetAccountInfo()
        {
            var response = await casperSdk.GetAccountInfo(account2.PublicKey);
            Console.WriteLine(response.Result.GetRawText());
            File.WriteAllText("res_GetAccountInfo.json", response.Result.GetRawText());
        }

        public async static Task PutString()
        {
            var sessionArgs = new List<NamedArg>();

            sessionArgs.Add(new NamedArg("name", CLValue.String("WorkingOn")));
            sessionArgs.Add(new NamedArg("value", CLValue.String("Friendly Hackaton")));

            var deploy = DeployTemplates.ContractCall("kvstorage_contract",
                "store_string",
                sessionArgs,
                account2,
                30000000000,
                "casper-net-1");
            deploy.Sign(account2);

            var response = await casperSdk.PutDeploy(deploy);

            string deployHash = response.GetDeployHash();
            var tokenSource = new CancellationTokenSource(TimeSpan.FromSeconds(120));
            response = await casperSdk.GetDeploy(deployHash, tokenSource.Token);

            Console.WriteLine(response.Result.GetRawText());
            File.WriteAllText("res_PutString.json", response.Result.GetRawText());
        }

        public async static Task ReadStringValue()
        {
            // Get the contract hash
            //
            var response = await casperSdk.GetAccountInfo(account2.PublicKey);
            var namedKeys = response.Result.GetProperty("stored_value").GetProperty("Account")
                .GetProperty("named_keys");
            string kvStorageHash = null;
            foreach (var nk in namedKeys.EnumerateArray())
            {
                if (nk.GetProperty("name").GetString().Equals("kvstorage_contract"))
                {
                    kvStorageHash = nk.GetProperty("key").GetString();
                    break;
                }
            }

            if (kvStorageHash == null)
                throw new Exception("Contract hash not found.");

            // now read the string querying for the WorkingOn key
            //
            response = await casperSdk.QueryState(kvStorageHash,
                new List<string>() {"WorkingOn"});

            Console.WriteLine(response.Result.GetRawText());
            File.WriteAllText("res_ReadString.json", response.Result.GetRawText());
        }

        public async static Task Main(string[] args)
        {
            var loggingHandler = new RpcLoggingHandler(new HttpClientHandler())
            {
                LoggerStream = new StreamWriter(Console.OpenStandardOutput())
            };
            casperSdk = new NetCasperClient(nodeAddress, loggingHandler);

            try
            {
                await FundAccount();
                await DeployKVStorageContract();
                await GetAccountInfo();
                await PutString();
                await ReadStringValue();
            }
            catch (RpcClientException e)
            {
                Console.WriteLine(e.RpcError.Message);
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
            }
        }
    }
}

`KeyValueStorageContract.csproj`

<Project Sdk="Microsoft.NET.Sdk">

    <PropertyGroup>
        <OutputType>Exe</OutputType>
        <TargetFramework>net5.0</TargetFramework>
    </PropertyGroup>

    <ItemGroup>
      <PackageReference Include="NetCasperSDK" Version="0.9.2" />
    </ItemGroup>

</Project>