Why stored procedure not working by button

Question

Greeting

 

I created a button,  when an Admin click on it call stored procedure to do this step:

===> Modify Column value [Bit] from true to False when a records came old than 30 days.

What happen?

when I click on button a page refresh, but a rows in table not modfiy ( change column value)

 

Button code:

protected void SChJ_Click(object sender, EventArgs e)
{
    string connectionString = @"Data Source=(local)\SQLEXPRESS;AttachDbFilename=|DataDirectory|\land.mdf;Integrated Security=True";
    using (SqlConnection sqlcon = new SqlConnection(connectionString))
    {
        try
        {
            sqlcon.Open();
            SqlCommand sqlcmd = new SqlCommand("get_expir_job_date", sqlcon);
            sqlcmd.CommandType = CommandType.StoredProcedure;
            sqlcmd.Parameters.AddWithValue("@C_date", SqlDbType.DateTime);
            sqlcmd.Parameters.AddWithValue("@JEnable", SqlDbType.Bit);
            sqlcmd.ExecuteNonQuery();
            sqlcon.Close();
        }
        catch (Exception ex)
        {
            JobFaUp.Text = ex.ToString();
        }
    }
}

Stored Procedure Code

CREATE PROCEDURE [dbo].[get_expir_job_date]
    @C_date datetime,  //Create Date
    @JEnable bit  //JOb Status Enable or Disable
AS
BEGIN
SELECT * FROM [Jobs]
Update [Jobs] SET @JEnable='False'
WHERE
@C_date  >  DATEADD(DAY, +30, CURRENT_TIMESTAMP)
End