Add Linq2GraphQL C# Client (graphql#1773)

Author: joadan

src/code/language-support/c-net/client/linq2graphql.md

@@ -0,0 +1,32 @@
+---
+name: Linq2GraphQL
+description: A straightforward Linq to GraphQL Client
+url: https://linq2graphql.com
+github: linq2graphql/linq2graphql.client
+---
+
+Linq2GraphQL generates C# classes from the GraphQL schema and and togheter with the nuget package Linq2GraphQL.Client it makes it possible to query the server using Linq expressions.
+
+A simple query that will get the first 10 orders with the primitive properties of orders and the connected customer
+```csharp
+var orders = await sampleClient
+    .Query
+        .Orders(first: 10)
+        .Include(e => e.Orders.Select(e => e.Customer))
+        .Select(e => e.Orders)
+        .ExecuteAsync();
+```
+
+An example mutation where we add a new customer and return the Customer Id.
+```csharp
+ var customerId = await sampleClient
+     .Mutation
+     .AddCustomer(new CustomerInput
+     {
+         CustomerId = Guid.NewGuid(),
+         CustomerName = "New Customer",
+         Status = CustomerStatus.Active
+     })
+     .Select(e=> e.CustomerId)
+     .ExecuteAsync();
+```