这样在一个sql里完成更新和插入，只用一次数据库连接，效率提高了

代码如下，请给出具体修改代码
 public void AddCategory(string nCategoryName, int nImgId, int nBelongToId, int nShopId, int nSortId)
    {
        int CategoryId = 0;
        string cmdText = "Select top 1 CategoryId from ProductCategory where CategoryName='' ROWLOCK";
        SqlConnection conn = new SqlConnection(Connection.ConnString);
        SqlCommand cmd = new SqlCommand(cmdText, conn);
        conn.Open();
        SqlTransaction tr = conn.BeginTransaction();
        cmd.Transaction = tr;
        try
        {
            SqlDataReader dr = cmd.ExecuteReader();
            if (dr.Read())
            {
                CategoryId = Int32.Parse(dr["CategoryId"].ToString());
            }
            dr.Close();
            if (CategoryId == 0)
            {
                cmd.CommandText = "INSERT ProductCategory(CategoryName,ImgId,BelongToId,ShopId,SortId) VALUES('" + nCategoryName + "','" + nImgId + "','" + nBelongToId + "','" + nShopId + "','" + nSortId + "')";
                cmd.ExecuteNonQuery();
            }
            else
            {
                cmd.CommandText = "Update ProductCategory Set CategoryName='" + nCategoryName + "',ImgId='" + nImgId + "',BelongToId='" + nBelongToId + "',SortId='" + nSortId + "',ShopId='" + nShopId + "' Where CategoryId=" + CategoryId;
                cmd.ExecuteNonQuery();
            }
            tr.Commit();
        }
        catch
        {
            tr.Rollback();
        }
        finally { conn.Close(); }
    }

你这样在并发多的时候很可能造成冲突的，直接用：
cmd.CommandText = @"Update ProductCategory set xxx where xxx
if @@ROWCOUNT = 0 
insert into ProductCategory  xxx";

这样在一个sql里完成更新和插入，只用一次数据库连接，效率提高了，并发可能也减小了

是sql，SqlServer支持同时执行多个sql的
后面直接cmd.ExecuteNonQuery();