如何从数据库中读取每行数据以及我在下面实现的方式是否正确？

Question

public partial class _Default : System.Web.UI.Page 
{ 
    protected void Button1_Click(object sender, EventArgs e) 
    {  
     if (TextBox1.Text == "" && TextBox2.Text == "" || TextBox1.Text == "") 
     {  
      Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "LoggedInScript", "alert('Plz Specify Username And Password'); window.location = 'Default.aspx';", true);     
     } 

     else if (TextBox2.Text == "") 
     { 
      Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "LoggedInScript", "alert('plz Specify Password'); window.location = 'Default.aspx';", true);     
     } 
     else 
     { 
      string connectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\\Samples\\login.mdb"; 

      OleDbConnection myConnection = new OleDbConnection(connectionString); 
      myConnection.Open(); 

      string query1 = "select * from LOGIN_TABLE"; 

      OleDbDataAdapter myAdapter = new OleDbDataAdapter(query1, myConnection); 
      DataSet loginData = new DataSet(); 
      myAdapter.Fill(loginData);  

      foreach (DataTable table in loginData.Tables) 
      {  
       foreach (DataRow row in table.Rows) 
       {       
        if (TextBox1.Text == row["UserName"].ToString() && TextBox2.Text == row["Password"].ToString()) 
        { 
         Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "LoggedInScript", "alert('Login SucessFull'); window.location = 'Default.aspx';", true); 
         break; 
        } 
        else 
        { 
         { 
          String a = TextBox1.Text; 
          String b = row["UserName"].ToString(); 
          Response.Write(a); 
          Response.Write(b); 
          Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "LoggedInScript", "alert('Login Failed'); window.location = 'Default.aspx';", true); 
          break; 
         } 
        } 
       } 
      } 
      myConnection.Close(); 
     }    
    } 
} 

Answer 1

还有很多该代码有误。

1. 使用WHERE子句
2. 循环遍历数据集的所有表选择一切从用户表，而不是过滤 - 仅1返回
3. 检查空的文本框，但允许空白的任何款额被接受
4. Txtspk in user messages。