Build a Solana Wallet Balance Checker API with (C#) .NET and Solnett

Published at

1/6/2025

Setting Up the Project

First, create a new web API project:

dotnet new web -n SolanaBalanceChecker
cd SolanaBalanceChecker

Next, let us install the required NuGet packages:

dotnet add package Solnet.Rpc
dotnet add package Solnet.Wallet
dotnet add package Microsoft.AspNetCore.OpenApi
dotnet add package Swashbuckle.AspNetCore

Understanding the Code

Let's break down our solution into key components:

1. Setting up the Dependencies

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

// Add Solana RPC client as a singleton
builder.Services.AddSingleton<IRpcClient>(sp => 
    ClientFactory.GetClient(Cluster.MainNet)
);

What are we doing here?

We're creating a minimal API application
Adding Swagger support for API documentation
Registering Solnet's RPC client as a singleton service
Configuring it to use Solana's MainNet (you can change this to TestNet or DevNet)

2. Creating the Balance Endpoint

app.MapGet("/balance/{walletAddress}", async (string walletAddress, IRpcClient rpcClient) =>
{
    try
    {
        // Validate wallet address format
        if (!Solnet.Wallet.PublicKey.IsValid(walletAddress))
        {
            return Results.BadRequest("Invalid Solana wallet address");
        }

        // Create public key from address
        var publicKey = new Solnet.Wallet.PublicKey(walletAddress);

        // Get the balance
        var balance = await rpcClient.GetBalanceAsync(publicKey);

Notes:

We create a GET endpoint that accepts a wallet address as a parameter
The address is validated using Solnet's built-in validator
We convert the address string to a PublicKey object
The RPC client is injected automatically thanks to dependency injection

3. Processing the Balance

if (balance.WasSuccessful)
{
    // Convert lamports to SOL (1 SOL = 1,000,000,000 lamports)
    decimal solBalance = balance.Result.Value / 1000000000m;

    return Results.Ok(new
    {
        Address = walletAddress,
        BalanceInSol = solBalance,
        BalanceInLamports = balance.Result.Value
    });
}

Important Details:

Solana balances are returned in lamports (1 SOL = 1,000,000,000 lamports)
We convert the balance to SOL for better readability
We return both SOL and lamports values for flexibility
The response is automatically serialized to JSON

At the end, your get request should look like this:

app.MapGet("/balance/{walletAddress}", async (string walletAddress, IRpcClient rpcClient) =>
{
    try
    {
        // Validate wallet address format
        if (!Solnet.Wallet.PublicKey.IsValid(walletAddress))
        {
            return Results.BadRequest("Invalid Solana wallet address");
        }

        // Create public key from address
        var publicKey = new Solnet.Wallet.PublicKey(walletAddress);

        // Get the balance
        var balance = await rpcClient.GetBalanceAsync(publicKey);

        if (balance.WasSuccessful)
        {
            // Convert lamports to SOL (1 SOL = 1,000,000,000 lamports)
            decimal solBalance = balance.Result.Value / 1000000000m;

            return Results.Ok(new
            {
                Address = walletAddress,
                BalanceInSol = solBalance,
                BalanceInLamports = balance.Result.Value
            });
        }
        else
        {
            return Results.Problem(
                detail: balance.Reason,
                statusCode: 500
            );
        }
    }
    catch (Exception ex)
    {
        return Results.Problem(
            detail: ex.Message,
            statusCode: 500
        );
    }
})
.WithName("GetBalance")
.WithOpenApi();

Test your API

Run your application:

dotnet run or dotnet watch run

Open your browser and navigate to:

https://localhost:5001/swagger

Try it out with a real Solana wallet address:

GET /balance/7xKXtg2CW87d97TXJSDpbD5jBkheTqA83TZRuJosgAsU

Example Response:

{
    "address": "7xKXtg2CW87d97TXJSDpbD5jBkheTqA83TZRuJosgAsU",
    "balanceInSol": 1.5,
    "balanceInLamports": 1500000000
}

Error Handling

catch (Exception ex)
{
    return Results.Problem(
        detail: ex.Message,
        statusCode: 500
    );
}

You'll receive clean error messages depending on the error:

Invalid wallet addresses
Network connection issues
RPC errors

Conclusion

Congrtatulation now have a working Solana wallet balance checker API built with .NET!.

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