如何比较数据库条目和表单条目

Question

我正在使用c＃2010 Express和SQL Compact。我有两列表和表单，用于添加数据以保存到表。但我不想拯救相同的条目。

例如;

Name     City
Sefa     Istanbul
Sefa     New york
Sefa     London
Ben      New York
......

.

是可以的，但如果用户想要添加另一个

Name     City
Sefa     Istanbul

.

或已有另一个条目，程序必须停止。

我已将此代码添加到我的项目中，但checkcmd.executenonquery（）命令始终返回'-1'

SqlCeConnection Baglanti = new SqlCeConnection(@"Data Source=|DataDirectory|\CeoDatabase.sdf;Password=CeoDB;Persist Security Info=True");
            Baglanti.Open();


            string checkcommand = "SELECT BarAdi, BarSehri FROM Barlar WHERE BarAdi = '"+ Txt_BarAdi.Text +"' AND BarSehri = '"+Txt_BarSehri.Text+"'";
            SqlCeCommand checkcmd = new SqlCeCommand(checkcommand, Baglanti);
            int kontrol = checkcmd.ExecuteNonQuery();
            MessageBox.Show(kontrol.ToString());
            return;
            if (checkcmd.ExecuteNonQuery() < 1)
            {
                MessageBox.Show("Bu bilgiler ile kayıtlı bir bar zaten mevcut");
                return;
            }
            else
            {
                SqlCeCommand Islem = new SqlCeCommand("INSERT INTO Barlar(BarAdi,BarSehri)VALUES('" + Txt_BarAdi.Text + "','" + Txt_BarSehri.Text + "')", Baglanti);
                Islem.ExecuteNonQuery();
                MessageBox.Show("İşlem başarıyla tamamlandı");
            }


            Baglanti.Close();

.

Answer 1

You can have it one of the ways

• Either set Unique Key for that column in Database . When new record will be inserted it will be automatically checked (Preferred)

• Or while Inserting new record check if that city already exist.

If you want to check for exist combination. Do somthing like this (I assume this how you have your data):

SqlCeConnection cn = new SqlCeConnection("your connection string");
string checkcommand = "SELECT [Name], [City] FROM [Tablename]" +
                      "WHERE [Name] == @name AND [City] == @city" ;
SqlCeCommand checkcmd= new SqlCeCommand(checkcommand, cn);
checkcmd.Parameters.AddWithValue("@name", txtBoxName.Text);
checkcmd.Parameters.AddWithValue("@city", txtBoxCity.Text);
cn.Open();
//Check if record already exist
if(checkcmd.ExecuteNonQuery() > 0)
{
    //It already exist
}
else
{
   //It doesn't exist Insert new record
}