小编the*_*mer的帖子

我的应用程序运行一些可能需要很长时间的数据库查询.

在执行这些查询时,我的应用程序似乎冻结,看起来应用程序已停止工作.

我需要使用进度条来避免这个问题,但我不确定如何预测查询执行所需的时间.

运行查询的代码如下

private void CheckSsMissingDate()
 {
  while (DateTime.Parse(time) <= DateTime.Now)
   {
     var ssCon = OpenSQLConnection();
     var cmd = new SqlCommand("SELECT TOP (1)Date_Time,Value1,Value2,Value3,Value4,Value5,Value6,
         "+ "Value7,Value8,Value9 from RAW_S001T01 where Date_Time >='" + tempTime + "'",ssCon);
     var dr = cmd.ExecuteReader();
     var count = 0;
     while (dr.Read())
      {
        ssChkDate = (dr["Date_Time"].ToString());
        conssChkDate = DateTime.Parse(ssChkDate).ToString("yyyy-MM-dd HH:mm:ss");
        tempTime = Convert.ToDateTime(ssChkDate);
        tempTime = tempTime.AddMinutes(15);
        TValue1 = (dr["Value1"].ToString());
        TValue2 = (dr["Value2"].ToString());
        TValue3 = (dr["Value3"].ToString());
        TValue4 = (dr["Value4"].ToString());
        TValue5 = (dr["Value5"].ToString());
        TValue6 = (dr["Value6"].ToString());
        TValue7 = (dr["Value7"].ToString()); …

我正在使用C#VS 2010开发一个应用程序.

我正在使用CE数据库.我从数据库中搜索字符串的代码是

string con = @"Data Source=|DataDirectory|\Database\Acadamy.sdf;Persist Security Info=False";
string cmd = "SELECT  sid AS [Student ID], sname AS [Student Name], contact AS [Contact No] FROM Student WHERE sname LIKE '%'+ @name +'%'";
var dt = new DataTable();
using (var a = new SqlCeDataAdapter())
{
 try
  {
   a.SelectCommand = new SqlCeCommand();
   a.SelectCommand.Connection = new SqlCeConnection(con);
   a.SelectCommand.CommandType = CommandType.Text;
   a.SelectCommand.CommandText = cmd;
   a.SelectCommand.Parameters.AddWithValue("@name", textBox1.Text);
   a.Fill(dt);
   dataGridView1.DataSource = dt;
  }
  catch (Exception ex)
   {
    MessageBox.Show(ex.Message);
   }
}

当我输入任何字符串时,as我收到错误System.FormatException: …

嗨我在C#中连接到MySQL,我需要检查是否打开了SQL连接.如果打开然后做某事或不做某事.我正在尝试下面的代码,但我收到错误.

var sqlCon= new SqlConnection(Properties.Settings.Default.sString);
var mySQLCon= new MySqlConnection(Properties.Settings.Default.dString);
sqlCon.Open();
mySQLCon.Open();
if (sqlCon.State==ConnectionState.Open && mySQLCon.State==ConnectionState.Open)
  {
    MessageBox.Show(@"Connection working.");
  }
else
  {
    MessageBox.Show(@"Please check connection string");
  }

我收到错误mySQLCon.State==ConnectionState.Open 错误是InvalidOperationException 我们如何检查MySQL连接状态.