How to build a registration seat allotment system in ASP.Net

I have used the Stored Procedure in this sample.

Please refer this.

HTML

<form id="form1" runat="server">
<div>
    Select the course
    <asp:DropDownList ID="ddlCourseTypes" runat="server">
    </asp:DropDownList>
    <br />
    Participant Name &nbsp;
    <asp:TextBox ID="txtParticipantName" runat="server" />
    <br />
    <asp:Button Text="Save" OnClick="Save" runat="server" />
</div>
</form>

Namespaces

using System.Configuration;
using System.Data.SqlClient;
using System.Data;

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        this.PopulateCourses();
    }
}

private void PopulateCourses()
{
    string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection conn = new SqlConnection(constr))
    {
        using (SqlCommand cmd = new SqlCommand("SELECT CourseId, CourseName FROM Courses", conn))
        {
            using (SqlDataAdapter da = new SqlDataAdapter(cmd))
            {
                DataTable ds = new DataTable();
                da.Fill(ds);
                ddlCourseTypes.DataTextField = "CourseName";
                ddlCourseTypes.DataValueField = "CourseId";
                ddlCourseTypes.DataSource = ds;
                ddlCourseTypes.DataBind();
                ddlCourseTypes.Items.Insert(0, new ListItem("Please Select", ""));
            }
        }
    }
}

protected void Save(object sender, EventArgs e)
{
    string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection conn = new SqlConnection(constr))
    {
        using (SqlCommand cmd = new SqlCommand("CourseAvailability", conn))
        {
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.Parameters.AddWithValue("@CourseType", this.ddlCourseTypes.SelectedItem.Value);
            cmd.Parameters.AddWithValue("@ParticipantName", this.txtParticipantName.Text.Trim());
            conn.Open();
            String message = cmd.ExecuteScalar().ToString();
            conn.Close();
            ScriptManager.RegisterClientScriptBlock(sender as Control, this.GetType(), "alert", "alert('" + message + "')", true);
        }
    }
}

Tables

CREATE TABLE [dbo].[Courses](
	[CourseId] [int] IDENTITY(1,1) NOT NULL,
	[CourseTotalSeat] [int] NOT NULL,
	[CourseAvailabelSeat] [int] NOT NULL,
	[CourseName] [varchar](50) NOT NULL
) ON [PRIMARY]

GO

INSERT INTO [Courses]
           ([CourseTotalSeat]
           ,[CourseAvailabelSeat]
           ,[CourseName])
     VALUES
           (4
           ,4
           ,'IT')
GO
INSERT INTO [Courses]
           ([CourseTotalSeat]
           ,[CourseAvailabelSeat]
           ,[CourseName])
     VALUES
           (3
           ,3
           ,'CS')
GO

CREATE TABLE [dbo].[Participants](
	[ParticipantId] [int] IDENTITY(1,1) NOT NULL,
	[CourseId] [int] NOT NULL,
	[ParticipantName] [varchar](50) NOT NULL
) ON [PRIMARY]

GO

 Stored Procedure

-- CourseAvailability 1,'Amir Shaikh'
CREATE PROCEDURE CourseAvailability
	@CourseType INT,
	@ParticipantName VARCHAR(50)
AS
BEGIN
	
	SET NOCOUNT ON;
	DECLARE @SeatCount INT
	SET @SeatCount = (SELECT CourseAvailabelSeat 
					  FROM Courses 
					  WHERE  CourseId = @CourseType)
	IF @SeatCount <> 0
	BEGIN
		INSERT INTO [Participants]([CourseId]
			   ,[ParticipantName])
		VALUES (@CourseType
				,@ParticipantName)
	    
		UPDATE [Courses] SET [CourseAvailabelSeat] = [CourseAvailabelSeat] - 1      
		WHERE  CourseId = @CourseType
		
		SELECT 'Data Inserted'
	END
	ELSE
	SELECT 'Seats are full'			
END
GO