C# OLEDB ExecuteReader 错误

Question

我对在 Visual Studio 中使用 M-S Access 数据库还很陌生，因此我不熟悉 OLEDB 语法。我设法使用各种互联网资源创建了这个程序。到目前为止，我的程序让用户登录登录表单，然后根据用户名和密码字段测试数据，如果它们匹配，则将用户重定向到第二个表单，然后使用名称从 Access 数据库收集数据他们已经登录，但是当它尝试执行从数据库收集数据的代码时，我不断收到错误“没有为一个或多个必需参数给出值。”他们的名字。到目前为止，这是我的代码：

private void Form2_Load(object sender, EventArgs e)
    {
        string username = lblName.Text;
        OleDbConnection con = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\Rhys\Documents\Visual Studio 2013\Projects\AssignmentTrackerV2\AssignmentTrackerV2\bin\Debug\ATDatabase.accdb");
        DataTable dt = new DataTable();
        con.Open();
        OleDbDataReader dr = null;
        OleDbCommand cmd = new OleDbCommand("SELECT [Name], [Surname], [Password], [ID] FROM MemberDetails WHERE [Name] = '" + username + "'", con);
//This is where the error is occuring.
        **dr = cmd.ExecuteReader();**
        while (dr.Read())
        {
            lblName.Text = (dr["Name"].ToString() + dr["Surname"].ToString());
            lblCourseTitle.Text = (dr["CourseTitle"].ToString());
            lblID.Text = "ID: " + (dr["MemberID"].ToString());
        }
        con.Close();
    }

任何关于如何修复此错误的建议将不胜感激，如前所述，我对 OLEDB 语法相当陌生，如果有简单的解决方案，我深表歉意，谢谢！

Answer 1

乍一看，这似乎应该可行。无论如何，你这样做的方式很糟糕，因为除其他外，它让你容易受到 SQL 注入攻击。尝试替换这个：

OleDbCommand cmd = new OleDbCommand("SELECT [Name], [Surname], [Password], [ID] FROM MemberDetails WHERE [Name] = '" + username + "'", con);

有了这个：

OleDbCommand cmd = new OleDbCommand("SELECT [Name], [Surname], [Password], [ID] FROM MemberDetails WHERE [Name] = @Name", con);

cmd.Parameters.AddWithValue("@Name", username);

如果还是不行，我们可以再仔细看看。

Answer 2

尝试使用此代码

     string username = lblName.Text;
    using(OleDbConnection con = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\Rhys\Documents\Visual Studio 2013\Projects\AssignmentTrackerV2\AssignmentTrackerV2\bin\Debug\ATDatabase.accdb"))
    {
         using(OleDbCommand cmd = new OleDbCommand(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\Rhys\Documents\Visual Studio 2013\Projects\AssignmentTrackerV2\AssignmentTrackerV2\bin\Debug\ATDatabase.accdb"))
         {
            cmd.Connection = con;
            cmd.CommandText = "SELECT [Name], [Surname], [Password], [ID] FROM MemberDetails WHERE [Name] = '" + username + "'";
            cmd.CommandType = CommandType.Text;
            OleDbDataReader dr = null;
            try 
            {           
                con.Open();
                dr = cmd.ExecuteReader();
                while (dr.Read())
                {
                   lblName.Text = (dr["Name"].ToString() + dr["Surname"].ToString());
                   lblCourseTitle.Text = (dr["CourseTitle"].ToString());
                   lblID.Text = "ID: " + (dr["MemberID"].ToString());
                }
                con.Close();
            }
            catch (Exception)
            {
                throw;
            }}}

希望这段代码对您有所帮助

C# OLEDB ExecuteReader 错误

C# OLEDB ExecuteReader Error

c#

oledb

ms-access