c# - 系统.InvalidOperationException : ExecuteReader: CommandText property has not been initialized Error is coming

Question

当我没有为登录用户定义 Usertype 时，我的 Gridview 工作正常。现在我的 BindGrid() 函数无法正常工作，并给我错误信息

System.InvalidOperationException: ExecuteReader: CommandText property has not been initialized Error is coming

下面是我的 BindGrid 代码:-

protected void BindGrid()
    {
        string username = string.Empty;
        string usertype = string.Empty;

        try
        {
            SqlConnection conn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["DefaultCSRConnection"].ConnectionString);
            SqlCommand cmd = new SqlCommand("SELECT usertype,username FROM tbl_User WHERE username='" + Session["User"].ToString() + "'", conn);
            conn.Open();
            SqlDataReader dr = cmd.ExecuteReader();
            if (dr.HasRows)
            {
                while (dr.Read())
                {
                    username = dr["username"].ToString();
                    usertype = dr["usertype"].ToString();
                }
            }
            conn.Close();

            string query = string.Empty;

            if (usertype == "0") // superadmin
            {
                query = "select Id,username,email,usertype,active,(CASE WHEN usertype='1' THEN 'Admin' WHEN usertype='0' THEN 'Super Admin' WHEN usertype='2' THEN 'User' END) AS UserRoleName from tbl_User ORDER By Id DESC";
            }
            if (usertype == "1") // admin
            {
                query = "select Id,username,email,usertype,active,(CASE WHEN usertype='1' THEN 'Admin' WHEN usertype='0' THEN 'Super Admin' WHEN usertype='2' THEN 'User' END) AS UserRoleName from tbl_User WHERE usertype != '0' ORDER By Id DESC";
            }
            if (usertype == "2") // user
            {
                query = "select Id,username,email,usertype,active,(CASE WHEN usertype='1' THEN 'Admin' WHEN usertype='0' THEN 'Super Admin' WHEN usertype='2' THEN 'User' END) AS UserRoleName from tbl_User WHERE username='" + username + "' ORDER By Id DESC";
            }

            cmd = new SqlCommand(query, conn);

            SqlDataAdapter da = new SqlDataAdapter(cmd);

            DataSet ds = new DataSet();
            da.Fill(ds);
            grdUser.DataSource = ds.Tables[0];
            grdUser.DataBind();
        }
        catch (Exception)
        {
            throw;
        }
    }

请指出这里有什么问题。

Answer 1

我推荐以下内容:

• Implement your code with the using statement
• Use parameterized SQL
• 确保您的初始查询返回一条记录且仅返回一条记录(您的循环将仅捕获最后遇到的username 和usertype)
• Implement the switch statement and ensure proper handling of the default case
• 确保您的连接已为您的第二个 SQL 查询打开
• 如果您只是重新抛出异常，则不需要 try/catch block 。