ParameterId is not inserting in a incremental order in sql

Question

My C# code

 

private string AutoIncrementID()

{

SqlConnection con = new SqlConnection();

myconn.Open();

SqlCommand cmd = new SqlCommand("Select *,ParameterId = 'P' + convert(varchar(10),row_number() over (partition by ItemId order by ParaId)) from tblMatParameter", myconn);

SqlDataReader dr = cmd.ExecuteReader();

string ParameterId = null;

if (dr.Read())

{

ParameterId = dr[0].ToString();

myconn.Close();

}

return ParameterId;

}

protected void Save(object sender, EventArgs e)

{

foreach (GridViewRow gvr in Gridview1.Rows)

{

//Connection

TextBox Parameter = gvr.FindControl("txtPara") as TextBox;

string txtPara = Parameter.Text;

string ParameterId = AutoIncrementID();

//int idLimit = 2;

string ParaNo = "" + ("P" + ParameterId);

SqlCommand cmd = new SqlCommand("INSERT INTO [ElixirERP].[ElixirAdmin].[tblMatParameter](ParameterId,Category,SubCategory,Brand,Item,Parameter,ItemId)" +

"VALUES('" + ParaNo + "',@ddlCategory,@ddlSubCategory,@ddlBrand,@ddlItem,'" + txtPara + "',(Select ItemId From [ElixirERP].[ElixirAdmin].[tblMatItem] where ItemId = '" + ddlItem.SelectedValue + "'))");

 

 Sql Table