从查询结果创建查询字符串

Question

在C#中我想运行一个SQL查询并将结果解析成一个QueryString传递给网页。在我的测试中，我正在尝试这样做，但我收到

错误

Key already exists

哪里不正确或正确的做法是什么？

private void PrepQuery()
{
    Dictionary<string, string> dictFormValues = new Dictionary<string, string>();
    string connectionString = null;
    SqlConnection cnn;
    SqlCommand cmd;
    StringBuilder sql = new StringBuilder();
    SqlDataReader reader;
    connectionString = "Data Source=server;Initial Catalog=database;User ID=;Password=";
    sql.Append("select employeename, employeeaddress, employeezip, employeecity, employeestate, employeephone ");
    sql.Append("from abcd ");
    sql.Append("where validated is not null ");
    cnn = new SqlConnection(connectionString);
    try
    {
        cnn.Open();
        cmd = new SqlCommand(sql.ToString(), cnn);
        reader = cmd.ExecuteReader();
        while (reader.Read())
        {
            dictFormValues.Add("employeename", reader.GetValue(0).ToString());
            dictFormValues.Add("employeeaddress", reader.GetValue(1).ToString());
            dictFormValues.Add("employeezip", reader.GetValue(2).ToString());
            dictFormValues.Add("employeecity", reader.GetValue(3).ToString());
            dictFormValues.Add("employeestate", reader.GetValue(4).ToString());
            dictFormValues.Add("employeephone", reader.GetValue(5).ToString());
            name = reader.GetValue(0).ToString();
        }
        reader.Close();
        cmd.Dispose();
        cnn.Close();
    }
    bool success = false;
    success = FormatForWebAPI();
    if (success = true; { GenerateEmail(); 
    if (sucess = false;) { ShowErrorOnScreen(); }
}

private void FormatForWebAPI();
{
    string strEndpointURL = string.Format("http://requestb.in/pm9rstuv/"); 
    System.Web.Script.Serialization.JavaScriptSerializer json = new System.Web.Script.Serialization.JavaScriptSerializer();
    foreach (var d in dictFormValues) { strPostData += d.Key + "=" + Server.UrlEncode(d.Value) + "&"; }
    strPostData += "hs_context=";
    System.Net.HttpWebRequest r = (System.Net.HttpWebRequest)System.Net.WebRequest.Create(strEndpointURL);
    r.Method = "POST";
    r.Accept = "application/json";
    r.ContentType = "application/x-www-form-urlencoded";
    r.ContentLength = strPostData.Length;
    r.KeepAlive = false;
    using (System.IO.StreamWriter sw = new System.IO.StreamWriter(r.GetRequestStream())) 
    { 
            try { sw.Write(strPostData); }
            catch { return false; }
    }
    return true;
}

Answer 1

基本上字典不允许重复键。来自 MSDN - Dictionary:

Every key in a Dictionary must be unique according to the dictionary's equality comparer.

在您的情况下，您要添加 'employeename'、'employeeaddress' 等作为字典的键。因此，从外观上看，如果您希望拥有超过 1 名员工（或数据行），那么您将收到此错误，对于每 1 名员工，它将尝试再次添加相同的键（员工姓名等）

根据我的评论尝试使用 Tuples such as a List<tuple<string, string>>. There are various other ways to store data, which contains duplicates such as in a DataTable 或可能在 xml 文档中。这真的取决于你真正掌握它后打算用它做什么。

或者创建您自己的 class 类型 'employee'，其中包含您要存储的所有信息（姓名、地址、邮政编码等）的属性，然后创建这些信息的列表，例如 List<employee>.

从查询结果创建查询字符串

Create Query String From Query Results

c#

asp.net

query-string