Getting Error as @Parameter1 is not a parameter for procedure

I am learning mvc from this video where I am getting data from a form and saving it to database. When I ran my code first it gave an error stating

Procedure or function ‘spAddEmployee’ expects parameter ‘@Employee_Name’, which was not supplied.

I followed a solution in which I initialized my stored procedure as NULL but now I am getting another error stating “@Parameter1 is not a parameter for procedure”.

This is my stored procedure

ALTER PROCEDURE [dbo].[spAddEmployee]
(
    @Employee_Name varchar(max) = NULL,
    @Employee_Age int = NULL,
    @Employee_Salary int = NULL,
    @Employee_City varchar(50) = NULL
)
AS
BEGIN
    INSERT INTO tblEmployee (Employee_Name, Employee_Age, Employee_Salary,  Employee_City)
    VALUES (@Employee_Name, @Employee_Age, @Employee_Salary, @Employee_City)
END

And this is my ADO.NET code:

public void AddEmployee(Employee employee)
{
    string connectionString = ConfigurationManager.ConnectionStrings["EmployeeContext"].ConnectionString;

    using (SqlConnection con = new SqlConnection(connectionString))
    {
        SqlCommand cmd = new SqlCommand("spAddEmployee", con)
        {
            CommandType = CommandType.StoredProcedure
        };

        SqlParameter paramName = new SqlParameter();
        paramName.ParameterName = "@Employee_Name";
        paramName.Value = employee.Employee_Name;
        cmd.Parameters.Add(paramName);

        SqlParameter paramAge = new SqlParameter();
        paramAge.ParameterName = "@Employee_Age";
        paramAge.Value = employee.Employee_Age;
        cmd.Parameters.Add(paramAge);

        SqlParameter paramSalary = new SqlParameter();
        paramSalary.ParameterName = "@Employee_Salary";
        paramSalary.Value = employee.Employee_Salary;
        cmd.Parameters.Add(paramSalary);

        SqlParameter paramCity = new SqlParameter();
        paramCity.ParameterName = "@Employee_City";
        paramCity.Value = employee.Employee_City;
        cmd.Parameters.Add(paramCity);

        con.Open();
        cmd.ExecuteNonQuery();
    }
}

And this is my controller code

[HttpPost]
[ActionName("Create")]
public ActionResult Create_Post(FormCollection formCollection)
{
    Employee employee = new Employee();
    employee.Employee_Name = formCollection["Employee_Name"];
    employee.Employee_Age = Convert.ToInt32(formCollection["Employee_Age"]);
    employee.Employee_Salary = Convert.ToInt32(formCollection["Employee_Salary"]);
    employee.Employee_City = formCollection["Employee_City"];
    
    EmployeeBuissnessLayer employeeBuissnessLayer = new EmployeeBuissnessLayer();
    employeeBuissnessLayer.AddEmployee(employee);
    return RedirectToAction("Index");
}

I am getting error at line

employeeBuissnessLayer.AddEmployee(employee);

Please help I have tried a lot of solutions but none of them have worked.

Answer

This

    SqlParameter paramName = new SqlParameter();
    paramName.ParameterName = "@Employee_Name";
    paramName.Value = employee.Employee_Name;
    cmd.Parameters.Add(paramName);

Should be

    SqlParameter paramName = new SqlParameter();
    paramName.ParameterName = "@Employee_Name";
    // Always set the datatype
    paramName.SqlDbType = SqlDbType.NVarChar;
    // For strings, always set the length
    paramName.Size = 128; // Max string length
    // Ensure you pass DBNull not C# null
    paramName.Value = employee.Employee_Name ?? System.DBNull.Value;
    cmd.Parameters.Add(paramName);

Note: its best practice not to name your Stored Procedure with the sp prefix.