MCP Server with .Net

--- title: MCP Server with .Net published: true description: Building a MCP Server with C# tags: dotnet,mcp,ai cover_image: https://dev-to-uploads.s3.amazonaws.com/uploads/articles/0kngrc72v2awjxz6qm6w.jpg # Use a ratio of 100:42 for best results. # published_at: 2026-03-12 21:50 +0000 --- With the [release 1.0 of the official ModelContextProtocol .Net SDK] (https://csharp.sdk.modelcontextprotocol.io), we are ready to make a MCP Server fully compliant with MCP specs and entirely in C#. As usually when I need to learn new stuffs I develop a simple demo around a real scenario. For the MCP Server I thought to build one for managing some data like customers, products and orders stored into a Postgres database. The MCP server provides the data on behalf of user prompt like: ```shell give me the customer list tell me the most expensive order how many USB-C Hub has been ordered ? give me the customer list without orders suggest a new product for the customer Jane Smith add new order ..... ``` The most important feature of MCP Server is the tool as function able to do something. Below an example of tool: ```cs [McpServerTool(Name = "GetCustomer"), Description("Retrieve a single customer from the database.")] public static async Task<object> GetCustomer(AppDbContext db, CancellationToken ct, ILogger<MCPTool> logger, [Description("Full name of the customer to retrieve.")] string fullName ){ logger.LogDebug( $"Executing GetCustomer tool with full name : {fullName }" ); var query = db.Customers.AsNoTracking(); var result = await query.Where(c => (c.FirstName + " " + c.LastName) == fullName) .FirstOrDefaultAsync(ct); if (result == null) return $"Customer with full name {fullName} not found."; return result; } ``` The example shows how to help llm to recognize the right tool by using specific custom attributes [McpServerTool]. Another interesting feature is the prompt. I implemented one to create a model capable of handling requests that require more complex and detailed context for responses. Here an example: ```cs [McpServerPrompt, Description("Generate product suggestion for new order prompt")] public static IEnumerable<ChatMessage> SuggestProductByCustomer( [Description("Full name of the customer")] string fullName ) { return [ new(ChatRole.System, "You are an assistant for an e-commerce platform. You help customers find products based on their preferences and past purchases."), new(ChatRole.User, $"Please suggest products for the customer with full name: {fullName}"), new(ChatRole.Assistant, "To suggest products for the customer, I will need to look up their past purchases and preferences in the database. I will use the GetCustomer and GetOrders tools to retrieve this information and then analyze it to find suitable product suggestions.") ]; } ``` The entire demo is available [here](https://github.com/antdimot/aiworkshop/tree/main/session3/mcpserver). It contains a dev setup environment which able to spin up quickly the Postgres database with already some test data. happy coding!