Question

    private void button1_Click(object sender, EventArgs e)
    {
        System.Data.OleDb.OleDbConnection conn = new System.Data.OleDb.OleDbConnection();
        // modify the connection string and include any additional required properties for your database
        conn.ConnectionString = @"Provider=Microsoft.Jet.OLEDB.4.0;" +
            @"Data Source=C:\Users\Dastgeer\Documents\Visual Studio 2013\Projects\UrduStemmerProject\UrduStemmerProject\Resources\ProjectDatbase.mdb";
        try
        {
            conn.Open();

            System.Data.OleDb.OleDbCommand cmd = new System.Data.OleDb.OleDbCommand(@"SELECT PreFix FROM UrduStemmerTbl WHERE (word = '"+InputWord+"')");
            cmd.Connection = conn;
            cmd.ExecuteNonQuery();

            System.Data.OleDb.OleDbCommand cmd2 = new System.Data.OleDb.OleDbCommand(@"SELECT Stem FROM UrduStemmerTbl WHERE (word = '" + InputWord + "')");
            cmd2.Connection = conn;
            cmd.ExecuteNonQuery();

            System.Data.OleDb.OleDbCommand cmd3 = new System.Data.OleDb.OleDbCommand(@"SELECT PostFix FROM UrduStemmerTbl WHERE (word = '" + InputWord + "')");
            cmd3.Connection = conn;
            cmd.ExecuteNonQuery();

            //Text boxes names are

            //prefixOutput.Text =;
            //stemOutput.Text = ;               
            //postfixOutput.Text = ;

            MessageBox.Show("Data Stemmed!");

        }
        catch (Exception ex)
        {
            MessageBox.Show("Failed to connect to data source");
        }
        finally
        {
            conn.Close();
        }
    }

Answer 1

您无需使用ExecuteNonQuery作为SELECT语句。此方法只执行您的查询，它不会返回任何数据或其他内容。

您的查询看起来只返回一行一行，您可以使用ExecuteScalar方法。

但更重要的是，您应该始终使用parameterized queries。这种字符串连接对SQL Injection攻击开放。

还可以使用using statement自动处理您的连接和命令，而不是手动调用Close方法。

顺便说一句，您可以将所有OleDbCommand个对象合并为一个，因为您在同一个表中查询不同的列。

using(var conn = new OleDbConnection(connString))
using(var cmd = conn.CreateCommand())
{
      cmd.CommandText = @"SELECT PreFix, Stem, PostFix FROM UrduStemmerTbl WHERE word = ?";
      cmd.Parameters.Add("?", OleDbType.VarWChar).Value = InputWord;
      // I assume your column type
      conn.Open();
      using(var dr = cmd.ExecuteReader())
      {
           if(dr.Read())
           {
              prefixOutput.Text = dr.GetString(0);
              stemOutput.Text = dr.GetString(1);
              postfixOutput.Text = dr.GetString(2);
           }
      }
}

如何将数据库查询数据添加到文本框中？

1 个答案: