Question

protected void Button1_Click1(object sender, EventArgs e)

  {
        string year = tb_year.Text;
        string gross = tb_gross.Text;
        string rating = DropDownList2.SelectedValue;
        string director = tb_director.Text;string sel = DropDownList1.SelectedValue;

 string query = "UPDATE MovieList SET ReleaseYear=@YearValue," +
                       "Gross=@GrossValue, Rating=@RatingValue," +
                       "Director=@DirectorValue WHERE Rank=@SelValue";

        System.Data.OleDb.OleDbCommand ocmd =
             new System.Data.OleDb.OleDbCommand(query,
             new System.Data.OleDb.OleDbConnection(CSTR));

        ocmd.Parameters.AddWithValue("@YearValue", year);
        ocmd.Parameters.AddWithValue("@GrossValue", gross);
        ocmd.Parameters.AddWithValue("@RatingValue", rating);
        ocmd.Parameters.AddWithValue("@DirectorValue", director);
        ocmd.Parameters.AddWithValue("@SelValue", sel);

        ocmd.Connection.Open();
        ocmd.ExecuteNonQuery();
        ocmd.Connection.Close();

    }

    protected void Button2_Click(object sender, EventArgs e)
    {

        string year = tb_year.Text;
        string gross = tb_gross.Text;
        string rating = DropDownList2.SelectedValue;
        string director = tb_director.Text;

        string sel = DropDownList1.SelectedValue;
        string query = "DELETE FROM MovieList WHERE Movie=" + DropDownList1.SelectedItem.Text + "'";

        System.Data.OleDb.OleDbCommand ocmd =
             new System.Data.OleDb.OleDbCommand(query,
             new System.Data.OleDb.OleDbConnection(CSTR));

        ocmd.Parameters.AddWithValue("@YearValue", year);
        ocmd.Parameters.AddWithValue("@GrossValue", gross);
        ocmd.Parameters.AddWithValue("@RatingValue", rating);
        ocmd.Parameters.AddWithValue("@DirectorValue", director);
        ocmd.Parameters.AddWithValue("@SelValue", sel);

        ocmd.Connection.Open();
        ocmd.ExecuteNonQuery();  <<***
        ocmd.Connection.Close();
        populateDropDowns();
    }
}
}

按钮1是更新按钮，当我更改值时，它可以更新数据库信息，此按钮可以立即更新信息。

但删除按钮，当我删除信息时，它会抛出一条错误信息：

＆＃34; OleDbException未被用户代码处理：附加信息：查询表达式中的语法错误（缺少运算符）＆＃39; Movie = The Matrix 转＆＃39;＆＃39 ;.在＆＃34; ***＆＃34;。

但是，当我再次打开此网站时，信息将被删除。如何解决此错误信息并立即删除信息？

Answer 1

以与更新相同的方式执行此操作，对where子句使用SQL参数。所以这段代码应该有效：

protected void Button2_Click(object sender, EventArgs e)
{
    string sel = DropDownList1.SelectedValue;

    // if your selection is empty, abort early
    if( sel == null || string.IsNullOrEmpty(sel.Text)) return;

    // use a SQL parameter like you did with update
    string query = "DELETE FROM MovieList WHERE Movie=@MovieValue";

    System.Data.OleDb.OleDbCommand ocmd =
         new System.Data.OleDb.OleDbCommand(query,
         new System.Data.OleDb.OleDbConnection(CSTR));

    // here the selected text for the movie is set to the movie parameter
    ocmd.Parameters.AddWithValue("@MovieValue", sel.Text);

    ocmd.Connection.Open();
    ocmd.ExecuteNonQuery();
    ocmd.Connection.Close();
    populateDropDowns();
}

Answer 2

byte[] encrypt = null;
byte [] decrypt = aesCipher2.doFinal(encrypt);

您应该使用上述内容更改查询，但缺少java.lang.IllegalArgumentException: Null input buffer

当我使用删除按钮时，我收到一条错误消息....如何解决这个问题？

2 个答案: