每次为真时，C＃bool行都会计入空列 [英] C# bool rows count with empty columns every time true

问题描述

i have 2 columns book1 and book2 to in borrowes table but some time users borrowed the book and some time no, so i need to delete user which not borrowed any book (book1 or book2). but i got every time value in True... let me know what can i do thanks. i tried this...

我尝试了什么：

What I have tried:

con.Open();

        bool readerHasRows = false;
        string brid = txtBr_id.Text;
        String syntax = "SELECT book1, book2 FROM Borrowes WHERE brId = @brid";
        using (SqlCommand cmd = new SqlCommand(syntax, con))
        {
            cmd.Parameters.AddWithValue("@brid", txtBr_id.Text);


            using (SqlDataReader reader = cmd.ExecuteReader())
            {
                readerHasRows = (!reader[0].IsDBNull);
            }
        }
        con.Close();

     if (readerHasRows == true)
        {
            MessageBox.Show("This borrower has borrowed the book please collect the book first.");
        }

推荐答案

使用SqlDataReader.HasRows属性（System.Data.SqlClient） [ ^ ]。

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