[Solved] If statement never executing in ASP.Net

insert statement not working, instead it updates even if the cylinder column is empty for the associated pid value

Label27.Text = "206";
protected void OnChckedChanged(object sender, EventArgs e)
{
    CheckBox chk = (CheckBox)sender;
    GridViewRow row = (GridViewRow)chk.NamingContainer;
 
    string number = row.Cells[2].Text;
    string pid = Label27.Text;
 
    string constring = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constring))
    {
        string acceptedCylinder = GetAcceptedCylinder(pid);
        if (chk.Checked)
        {
            if (string.IsNullOrEmpty(acceptedCylinder))
            {
                using (SqlCommand cmd = new SqlCommand("INSERT INTO issuesheet (cylinders) VALUES(@cylinders) ", con))
                {
                   
                    cmd.Parameters.AddWithValue("@cylinders", "{'" + number.Trim() + "'}");
                    con.Open();
                    cmd.ExecuteNonQuery();
                    con.Close();
                }
                ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "alertMessage", "alert('Record inserted successfully.')", true);
            }
            else
            {
                List<string> cylinderNo = acceptedCylinder.Replace("{", "").Replace("}", "").Replace("'", "").Split(',').ToList();
                cylinderNo.Add(number);
                using (SqlCommand cmd = new SqlCommand("UPDATE issuesheet SET cylinders = @cylinders where pid='" + Label27.Text + "'", con))
                {
                 
                    cmd.Parameters.AddWithValue("@cylinders", "{'" + string.Join("','", cylinderNo.Distinct()) + "'}");
                    con.Open();
                    cmd.ExecuteNonQuery();
                    con.Close();
                }
                ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "alertMessage", "alert('Record updated successfully.')", true);
            }
        }
        else
        {
            if (!string.IsNullOrEmpty(acceptedCylinder))
            {
                List<string> cylinderNo = acceptedCylinder.Replace("{", "").Replace("}", "").Replace("'", "").Split(',').ToList();
                cylinderNo.Remove(number);
                using (SqlCommand cmd = new SqlCommand("UPDATE issuesheet SET cylinders = @cylinders where pid='" + Label27.Text + "' ", con))
                {
                    cmd.Parameters.AddWithValue("@cylinders", "{'" + string.Join("','", cylinderNo.Distinct()) + "'}");
                    con.Open();
                    cmd.ExecuteNonQuery();
                    con.Close();
                }
                ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "alertMessage", "alert('Record Deleted successfully')", true);
            }
        }
    }
}
 
private string GetAcceptedCylinder(string pid)
{
    string acceptCylinder = "";
    string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constr))
    {
        using (SqlCommand cmd = new SqlCommand())
        {
            cmd.CommandText = "SELECT cylinders FROM issuesheet WHERE pid=@pid ";
            cmd.Connection = con;
            cmd.Parameters.AddWithValue("@pid", Label27.Text);
            con.Open();
            acceptCylinder = Convert.ToString(cmd.ExecuteScalar());
            con.Close();
        }
    }
 
    return acceptCylinder;
}

CREATE TABLE [dbo].[issuesheet](
    [id] [int] IDENTITY(1,1) NOT NULL,
    [pid] [int] NULL,
    [machine] [nvarchar](255) NULL,
    [orderquantity] [float] NULL,
    [workdocket] [nvarchar](50) NULL,
    [cylinders] [nvarchar](255) NULL,
    [dies] [nvarchar](255) NULL,
    [embossings] [nvarchar](255) NULL,
    [inks] [nvarchar](255) NULL,
    [ints] [nvarchar](255) NULL,
    [comment] [nvarchar](255) NULL,
    [solvents] [nvarchar](255) NULL
) ON [PRIMARY]
GO
SET IDENTITY_INSERT [dbo].[issuesheet] ON
GO
INSERT [dbo].[issuesheet] ([id], [pid], [machine], [orderquantity], [workdocket], [cylinders], [dies], [embossings], [inks], [ints], [comment], [solvents]) VALUES (1, 206, N'machine', 67543, N'bbbbb', N'[]', N'[]', N'[]', N'[]', NULL, NULL, N'[]')
GO
SET IDENTITY_INSERT [dbo].[issuesheet] OFF
GO
ALTER TABLE [dbo].[issuesheet] ADD  DEFAULT ('[]') FOR [cylinders]
GO
ALTER TABLE [dbo].[issuesheet] ADD  DEFAULT ('[]') FOR [dies]
GO
ALTER TABLE [dbo].[issuesheet] ADD  DEFAULT ('[]') FOR [embossings]
GO
ALTER TABLE [dbo].[issuesheet] ADD  DEFAULT ('[]') FOR [inks]
GO
ALTER TABLE [dbo].[issuesheet] ADD  DEFAULT ('[]') FOR [solvents]
GO

please help