Question

实际上，我想单击按钮并以一次性方式执行这两个查询。

string Query = "UPDATE harga_semasa SET we_buy='" + this.textBox1.Text + "',we_sell='" + this.textBox2.Text + "', idharga_semasa='" + this.label5.Text + "' WHERE type='" + this.label1.Text + "';";
string Query2 = "UPDATE harga_semasa SET we_buy='" + this.textBox3.Text + "',we_sell='" + this.textBox4.Text + "', idharga_semasa='" + this.label10.Text + "' WHERE type='" + this.label4.Text + "';";

MySqlConnection MyConn2 = new MySqlConnection(ConString);
MySqlCommand MyCommand2 = new MySqlCommand(Query2, MyConn2);
MySqlCommand MyCommand1 = new MySqlCommand(Query, MyConn2);
MySqlDataReader MyReader2;
MyConn2.Open();
MyReader2 = MyCommand2.ExecuteReader();
MyReader2 = MyCommand1.ExecuteReader();
MessageBox.Show("Data Updated");
while (MyReader2.Read())
{
}
MyConn2.Close();

如何使用此代码执行多个？我尝试将一些数据添加到已插入的现有表中。我是C＃的新手，开始了解一些代码。

Answer 1

您不能同时对多个MySqlDataReader对象重新使用同一连接：https://mysqlconnector.net/troubleshooting/connection-reuse/

由于您的代码实际上不需要MySqlDataReader，因此一个简单的解决方法是使用ExecuteNonQuery执行您的UPDATE语句。

您还应该使用参数化查询来避免SQL注入和using语句自动关闭连接

using (var connection = new MySqlConnection(ConString))
{
    connection.Open();

    using (var command = new MySqlCommand(@"UPDATE harga_semasa SET we_buy=@we_buy, we_sell=@we_sell, idharga_semasa=@idharga_semasa WHERE type=@type;", connection)
    {
        command.Parameters.AddWithValue("@we_buy", this.textBox1.Text);
        command.Parameters.AddWithValue("@we_sell", this.textBox2.Text);
        command.Parameters.AddWithValue("@idharga_semasa ", this.label5.Text);
        command.Parameters.AddWithValue("@type", this.label1.Text);

        // use this to run the query (without MySqlDataReader)
        command.ExecuteNonQuery();
    }

    // execute your second query the same way here

    MessageBox.Show("Data Updated");
}

如何在C＃中执行多字符串SQL命令

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