Introduction

A smart contract is a computer program where the parties have consent on predetermined conditions of the agreement. Smart contract stores and self-executes in the blockchain network. It runs when the predefined conditions are met. Smart Contract allows transactions to be made without the need for a middleman and those transactions are irreversible, transparent, and traceable. This article explains how we can write a Smart Contract in .NET 6 Framework as well as demonstrate with an example of smart contract code.

There are two ways to develop Stratis Smart Contract using C# language:

  • Using VS Code
  • Using Visual Studio

However, in this article, we will use Visual Studio to develop the Smart Contract in .NET6. Additionally, we will see the differences in developing the Smart Contract in .NET Core 3.1 and .NET 6. Overall, you will get ideas and differences between Smart Contract coding in .NET Core and .Net 6.

In this article, we will focus on Contract development in .NET 6. To get more info about getting started with Contract development, and deployment with all tools and steps for developers you can refer to previous articles here:

Prerequisites

  • Visual Studio 2022
  • Knowledge of C#

Smart Contract in .NET Core 3.1

Let’s take an example of the Stratis Hello World Contract code. Below is the code of the Hello World contract in .NET Core. In Blockchain, we store the data in key and value pairs, for that we use C# property getter and setter in Smart Contract code.

using Stratis.SmartContracts;

[Deploy]
public class HelloWorld : SmartContract
{
    private string Greeting
    {
        get 
        {
            return this.PersistentState.GetString("Greeting");
        }
        set
        {
            this.PersistentState.SetString("Greeting", value);
        }
    }

    public HelloWorld(ISmartContractState smartContractState)
        : base(smartContractState)
    {
        this.Greeting = "Hello World!";
    }

    public string SayHello()
    {
        return this.Greeting;
    }
}

In .NET Core, we can use PersistentState to store the key-value pair. The above code validates and compiles successfully without any error or warning when we use .NET Core framework.

However, in .NET 6 PersistentState is obsolete. Where we must use State property. If you write the same Hello World Code in .NET6 framework you will get the below warnings.

Additionally, even if you ignore and try to validate and compile the code using the Stratis Smart Contract tool, it will not be able to compile the code and you will get a compilation error as depicted below.

Not that, once the Smart contract code is ready, we need to validate and then compile it to the byte code and that generated byte code must be deployed on the blockchain.

Smart Contract Tool: The smart contract tool is powered by the Stratis platform which is used to validate and generate the byte code of the Smart contract. Smart Contract Tool (Sct) is used to validate for determinism and format of the contract as well as compile the Contract code. Smart Contract tool is a command line tool and it is also written in C#. You can download the Sct tool from here.

Now, let’s move to Smart Contract Development in .NET6

Getting Started with Smart Contract in .NET 6

Step 1– Open Visual Studio and click on create a new project.

Step 2– Select a class library project in C# as illustrated below and click on Next.        

Step 3– Give the project name and directory of the project as usual.

Step 4– Select Framework .NET 6 as shown below and Click on Create. The default empty class library project will be created as illustrated below.

Step 5- Now, we will install NuGet Package for Stratis Smart contract development in .NET 6. You can use the Nuget package manager console to install as usual or can use NuGet Package Manager and install from there.

Open the package manager console as shown below.

Then run the below command in the Package manager console to install Smart Contract NuGet Package for .NET 6. This package is designed for Dotnet 6 framework. You need to be careful while installing this package, so opt for the right package for .NET 6.

Install-Package Stratis.SmartContracts.NET6

Step 6– Right click on the project and add a new class as shown below.

Step 7– Now, let’s get the existing HelloWorld contract code from here.

And paste it into the HelloWorld class of this project. Once you paste the code you will get the information in the code as shown below.


Warning: ‘SmartContract.PersistentState’ is obsolete: ‘Please use State property as shorthand’. So, we can’t use PersistenceState in .NET6.
Even if we try to validate and compile the contract code using Sct tool the validation will be failed. So we need to change the PersistenceState to State in the code first then only validation will be succeeded.
Thus, HelloWorld contract new code in .NET 6 will be as below.
using Stratis.SmartContracts;

/// <summary>
/// A basic "Hello World" smart contract
/// </summary>
[Deploy]
public class HelloWorld : SmartContract
{
    private string Greeting
    {
        get
        {
            return this.State.GetString("Greeting");
        }
        set
        {
            this.State.SetString("Greeting", value);
        }
    }

    public HelloWorld(ISmartContractState smartContractState)
        : base(smartContractState)
    {
        this.Greeting = "Hello World!";
    }

    public string SayHello()
    {
        return this.Greeting;
    }

}

Now, we have a warning and error-free HelloWorld contract code in .NET 6. It’s time to validate and compile the contract code using the Stratis Smart Contract tool. You can follow the same steps to validate and compile the code and then can deploy the byte code on the Stratis Blockchain as like the earlier article from here and deployment and interaction from here. Once, deployed we can interact with the contract using the contract address, and methods from any application. The deployed contract can be called or used in any software system for this you can reference my previous article where I demonstrated how we can call a contract from ASP.NET Core Application.  

Conclusion

Hence, in this article, we learned how to develop the Smart Contract in .NET 6 as well as How the .NET 6 Smart Contract is different from .NET Core. Moreover, we learn the obsolete property of PersistenceState in .NET 6 and it’s replacement to manage the key-value pair state on the Blockchain network with an example of HelloWorld Contract.

If you are interested to explore the Stratis Sample Smart Contracts in .NET 6, you can get the sample contract code for .NET 6 from here.

More content on learning Blockchain for .NET developers can be found in Stratis Academy

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