In this article I will explain with an example, how to use Output Parameter with Stored Procedure using Dapper library in ASP.Net Core Razor Pages.
Note: For more details on ASP.Net Core 7 Razor Pages, please refer my article ASP.Net Core 7 Razor Pages: Hello World Tutorial with Sample Program example.
 
 

Installing Dapper package using Nuget

In order to install Dapper library using Nuget, please refer my article Install Dapper from Nuget in Visual Studio.
 
 

Database

I have made use of the following table Customers with the schema as follows.
Using Output Parameter with Stored Procedure using Dapper in ASP.Net Core Razor Pages
 
Note: You can download the database table SQL by clicking the download link below.
         Download SQL file
 
 

Stored Procedure

The following Stored Procedure will be used to Insert data into the SQL Server database table.
This Stored Procedure accepts following parameters which are used to insert the records:
Name – This is an INPUT Parameter to pass the Name of the Customer.
Country – This is an INPUT Parameter to pass the Country of the Customer.
CustomerId – This is an OUTPUT Parameter to get the last inserted CustomerId.
Note: Output Parameter is identified by the keyword OUTPUT.
 
CREATE PROCEDURE [Customers_InsertCustomer_Output]
      @Name VARCHAR(100),
      @Country VARCHAR(50),
      @CustomerId INT OUTPUT
AS
BEGIN
    INSERT INTO [Customers]
               ([Name]
               ,[Country])
    VALUES
               (@Name
               ,@Country)
 
    SELECT @CustomerId = SCOPE_IDENTITY()
END
 
 

Model

The Model class consists of following properties.
public class CustomerModel
{
    public int CustomerId { get; set; }
    public string Name { get; set; }
    public string Country { get; set; }
}
 
 

Namespaces

You will need to import the following namespaces.
using Dapper;
using System.Data;
using System.Data.SqlClient;
 
 

Razor PageModel (Code-Behind)

The PageModel consists of following Handler method.

Handler method for handling GET operation

This Handler method is left empty as it is not required.
 

Handler method for handling POST operation

This Handler method accepts CustomerModel class object as a parameter.
Inside this Handler method, first the connection string is read from the ConnectionStrings section of the AppSettings.json file.
An object of DynamicParameters is created and CustomerId is added as parameter with its Data Type specified and its Direction is set to Output since by default the Direction of all parameters are Input.
The Name and Country values are also added as parameter.
Then, the Execute method of Dapper library is used to fetch CustomerId of the inserted record from the Customers Table.
Note: For more details on Execute method, please refer my article Understanding Dapper Execute in C# and VB.Net.
 
The CustomerId of the inserted record i.e. the Output parameter value is fetched using Get method of DynamicParameters class.
Finally, the CustomerId of the inserted record is set into the public property of CustomerModel class.
public class IndexModel : PageModel
{
    public CustomerModel Customer { get; set; }
    public IConfiguration Configuration { get; set; }
 
    public IndexModel(IConfiguration _configuration)
    {
        this.Configuration = _configuration;
    }
 
    public void OnGet()
    {
    }
 
    public void OnPostSubmit(CustomerModel customer)
    {
        string spName = "Customers_InsertCustomer_Output";
        string constr = this.Configuration.GetSection("ConnectionStrings")["MyConn"];
        using (SqlConnection con = new SqlConnection(constr))
        {
            DynamicParameters dynamicParameters = new DynamicParameters();
            // Adding Input parameters.
            dynamicParameters.Add("@Name", customer.Name);
            dynamicParameters.Add("@Country", customer.Country);
            // Adding Output parameter.
            dynamicParameters.Add("@CustomerId", DbType.Int32, direction: ParameterDirection.Output);
            con.Execute(spName, dynamicParameters, commandType: CommandType.StoredProcedure);
            customer.CustomerId = dynamicParameters.Get<int>("@CustomerId");
            this.Customer = customer;
        }
    }
}
 
 

Razor Page (HTML)

Inside the Razor Page, the ASP.Net TagHelpers is inherited.
The HTML of Razor Page consists of an HTML Form consisting of an HTML Table which consists of an HTML INPUT TextBox and an HTML SELECT element (DropDownList) and a Submit Button.
The Submit Button has been set with the POST Handler method using the asp-page-handler attribute.
Note: In the Razor PageModel, the Handler method name is OnPostSubmit but here it will be specified as Submit when calling from the Razor HTML Page.
 
Inside the View, the following jQuery script file is inherited.
1. jquery.min.js
 

Submitting Form

When the Submit button is clicked the Form is submitted and finally, the Model is checked for NULL and if it is not NULL then, the value of the CustomerId is displayed using JavaScript Alert Message Box.
@page
@model Dapper_Output_Parameter_SP_Core_Razor.Pages.IndexModel
@addTagHelper*, Microsoft.AspNetCore.Mvc.TagHelpers
@{
    Layout = null;
}
 
<!DOCTYPE html>
 
<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Index</title>
</head>
<body>
    <form method="post">
         <table cellpadding="0" cellspacing="0">
             <tr>
                 <td>Name: </td>
                 <td><input type="text" asp-for="Customer.Name" /></td>
             </tr>
             <tr>
                 <td>Country: </td>
                 <td>
                     <select asp-for="Customer.Country">
                         <option value="Please select">Please select</option>
                         <option value="United States">United States</option>
                         <option value="India">India</option>
                         <option value="France">France</option>
                         <option value="Russia">Russia</option>
                     </select>
                 </td>
             </tr>
             <tr>
                 <td></td>
                 <td><input type="submit" value="Submit" asp-page-handler="Submit" /></td>
             </tr>
          </table>
    </form>
    <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.7.1/jquery.min.js"></script>
    @if (Model.Customer != null)
    {
        <script type="text/javascript">
            $(function () {
                alert("Inserted Customer ID: " + @Model.Customer.CustomerId);
            });
        </script>
    }
</body>
</html>
 
 

Screenshots

The Form

Using Output Parameter with Stored Procedure using Dapper in ASP.Net Core Razor Pages
 

Record after Insert in database

Using Output Parameter with Stored Procedure using Dapper in ASP.Net Core Razor Pages
 
 

Downloads

Download Code