我有一个检查按钮,可以在组合框中获取月份和年份:
private void cmdSend_Click(object sender, System.EventArgs e)
{
List<string>[] list;
list = dbConnect.Select(month_list.SelectedItem.ToString(), year_list.SelectedItem.ToString());
printer_info.Rows.Clear();
for (int i = 0; i < list[0].Count; i++)
{
int number = printer_info.Rows.Add();
printer_info.Rows[number].Cells[0].Value = list[0][i];
printer_info.Rows[number].Cells[1].Value = list[1][i];
printer_info.Rows[number].Cells[2].Value = list[2][i];
printer_info.Rows[number].Cells[3].Value = list[3][i];
}
}
然后,检查按钮将月份和年份传递给select语句函数:
public List<string>[] Select(string month,string year)
{
string query = "SELECT * FROM page_counter WHERE month = '@month' AND year = @year;";
//Create a list to store the result
List<string>[] list = new List<string>[4];
list[0] = new List<string>();
list[1] = new List<string>();
list[2] = new List<string>();
list[3] = new List<string>();
//Open connection
if (this.OpenConnection() == true)
{
//Create Command
MySqlCommand cmd = new MySqlCommand(query, connection);
cmd.Parameters.Add("@month",MySqlDbType.VarChar);
cmd.Parameters.Add("@year", MySqlDbType.Year);
cmd.Parameters["@month"].Value = month;
cmd.Parameters["@year"].Value = year;
//Create a data reader and Execute the command
MySqlDataReader dataReader = cmd.ExecuteReader();
//Read the data and store them in the list
while (dataReader.Read())
{
list[0].Add(dataReader["id"].ToString() + "");
list[1].Add(dataReader["month"].ToString() + "");
list[2].Add(dataReader["year"].ToString() + "");
list[3].Add(dataReader["page_count"].ToString() + "");
}
//close Data Reader
dataReader.Close();
//close Connection
this.CloseConnection();
//return list to be displayed
return list;
}
然后数据将显示在gridview上,默认情况下在页面设计器中指定所有列:
当我运行代码时,它没有任何错误,但gridview上没有显示任何值。我犯了什么错误?我是c#winform的新手,请指教。
答案 0 :(得分:1)
我认为你有两个错误。首先你应该从查询字符串中删除single-quotes
:
string query = "SELECT * FROM page_counter WHERE month = @month AND year = @year;"
因为当你使用单引号时你的参数名称被视为实际值。其次,我强烈建议你使用一个类而不是List<string>[]
。该类看起来像这样:
public class Data
{
public int Id { get; set; }
public string Month { get; set; }
public string Year { get; set; }
public int PageCount { get; set; }
}
然后创建一个List<Data>
并按如下方式填充:
var dataList = new List<Data>();
while (dataReader.Read())
{
var item = new Data();
item.Id = Convert.Toınt32(dataReader["id"]);
item.Month = dataReader["month"].ToString();
item.Year = dataReader["year"].ToString();
item.PageCount = Convert.ToInt32(dataReader["page_count"]);
dataList.Add(item);
}
return dataList;
然后当然改变你的方法的返回类型:
public List<Data> Select(string month,string year)
然后您需要做的就是设置DataSource
属性:
var list = dbConnect.Select(month_list.SelectedItem, year_list.SelectedItem);
printer_info.DataSource = list;