web api insert function

use HttpClient as shown below

public void Save()  
{  
static HttpClient client = new HttpClient();  
 client.BaseAddress = new Uri("http://localhost:4354/api/");  
 client.DefaultRequestHeaders.Accept.Clear();  
 client.DefaultRequestHeaders.Accept.Add(  
  new MediaTypeWithQualityHeaderValue("application/json"));  
  
var product = new Product() { Name = txtProd.Text Price = txtPrice.Text, Category = txtcat.Text };  
 var response = await client.PostAsJsonAsync("products", product); // here //products is the controller(Endpoint) name  
}  

for creating api follow my article :- https://www.sharpencode.com/article/WebApi/implementing-crud