命令执行期间遇到致命错误

Question

我正在尝试检查已输入的用户名是否已存在于数据库中。但高于错误率。

protected void txtUsername_TextChanged(object sender, EventArgs e)
        {
            MySqlConnection con = new MySqlConnection(con1);
        try{
        if (!string.IsNullOrEmpty(txtUsername.Text))
        {


            con.Open();
            MySqlCommand cmd = new MySqlCommand("select username from client_login where username=@Name", con);
            DataSet ds = new DataSet();

            MySqlDataReader dr = cmd.ExecuteReader();

            if (dr.HasRows)
            {
                checkusername.Visible = true;
                imgstatus.ImageUrl = "NotAvailable.jpg";
                lblStatus.Text = "UserName Already Taken";
            }
            else
            {
                checkusername.Visible = true;
                imgstatus.ImageUrl = "Icon_Available.gif";
                lblStatus.Text = "UserName Available";
            }
        }
        else
        {
            checkusername.Visible = false;
        }
        con.Close();
        }

        catch(Exception ex){
            Response.Write(ex);
        }

    }   

和textBox代码是

` <asp:TextBox ID="txtUsername" runat="server" AutoPostBack="true" OnTextChanged="txtUsername_TextChanged"></asp:TextBox>`

错误在Execute Reader as base = {＆＃34;命令执行期间遇到致命错误。＆＃34;}

Answer 1

您需要在sql查询中填充参数。像：

cmd.Parameters.AddWithValue("@Name", txtUsername.Text);