SQL值转换为整数

Question

I'm trying to compare values in a database that are updated every time a user logs in. When I execute a query with the given code nothing happens. However if I give it a value of say (where Attempt >10) it works where am I going wrong?

private void User_Tick(object sender, EventArgs e)
{
    SqlConnection con13 = new SqlConnection("Data Source = *** ")

    SqlDataAdapter SDA2 = new SqlDataAdapter("SELECT [User],[Login],[number1],[number2],[number3],[Alertcount] FROM Users.dbo.[Email] where [Alertcount] = 1 and [Alertcount] !=2", con13);

    DataTable Users = new DataTable();
    DataTable DATA2 = new DataTable();

    SDA2.Fill(DATA2);

    dataGridView2.DataSource = DATA2;

    foreach (DataGridViewRow dr in dataGridView2.Rows)
    {
        string col2 = 1.Cells["User"].Value.ToString();
        string col1 = 1.Cells["Login"].Value.ToString();
        string col3 = 1.Cells["number1"].Value.ToString();
        string col4 = 1.Cells["number2"].Value.ToString();
        string col5 = 1.Cells["number3"].Value.ToString();
        string col6 = 1.Cells["Alertcount"].Value.ToString();

        var mine = Convert.ToInt32(col3);
        var mine2 = Convert.ToInt32(col5);

        SqlConnection CON2 = new SqlConnection("Data Source = ***")
        CON2.Open();

        SqlDataAdapter SDA = new SqlDataAdapter("SELECT [User],[Login],[Attempt] FROM User.dbo.Actions where  [Attempt] >  '"+mine+ "' and [Attempt] < '" + mine2 + "'", CON2);

        DataTable DATA = new DataTable();
        SDA.Fill(DATA);

        dataGridView1.DataSource = DATA;
    }
}

Answer 1

If column Attempt is an integer (as evident from the fact that Attempt < 10 runs), you need not pass comparison values to it in string. So your query should be like this:

SqlDataAdapter SDA = new SqlDataAdapter("SELECT [User],[Login],[Attempt] FROM User.dbo.Actions where  [Attempt] >  "+mine+ " and [Attempt] < " + mine2 , CON2);

I would suggest you to debug such errors in future by creating a query variable and then running the query in SQL manually to see what the error is. You could do something like this:

var query = "SELECT [User],[Login],[Attempt] FROM User.dbo.Actions where  [Attempt] >  "+mine+ " and [Attempt] < " + mine2 ;
SqlDataAdapter SDA = new SqlDataAdapter(query , CON2);

Answer 2

nothing happens - not enough information for correct answer. If actually nothing happens, then remove all try catch blocks you have around code and run application again. Then if something wrong you will get very useful information about what gone wrong in the form of Exception .

However, problem seems is that you passing wrong data to database query.
Always use SqlParameter for passing dynamic data to the query. SqlParameter have type which you can set to correspondent type of column you want operate on. Also SqlParameter will protect you from sql injection.

Use using for disposable objects when ever it possible (read "always")

var emailQuery = 
    @"SELECT [User] ,[Login] ,[number1] ,[number2] ,[number3] ,[Alertcount] 
    FROM Users.dbo.[Email] 
    WHERE [Alertcount] = 1 
        AND [Alertcount] !=2"; // Useless condition, because Alertcount already = 1

using(var connection2 = new SqlConnection("Data Source = *** "))
using(var adapter2 = new SqlDataAdapter(emailQuery, connection1))
{
    var data2 = new DataTable();
    adapter2.Fill(data2);
    dataGridView2.DataSource = data2;
}

var actionsQuery = 
    @"SELECT [User] ,[Login] ,[Attempt] 
    FROM User.dbo.Actions 
    WHERE Attempt > @Mine AND Attempt < @Mine2";
foreach (var row in dataGridView2.Rows)
{
    var mine = (int)row.Cells["number1"].Value; // it is already integer, just cast it
    var mine2 = (int)row.Cells["number3"].Value;

    using(var connection1 = new SqlConnection("Data Source = *** "))
    using(var adapter1 = new SqlDataAdapter(actionsQuery, connection1))
    {
        var parameters = new[]
        {
            new SqlParameter
            {
                ParameterName = "@Mine",
                SqlDbType = SqlDbType.Int,
                Value = mine
            },
            new SqlParameter
            {
                ParameterName = "@Mine2",
                SqlDbType = SqlDbType.Int,
                Value = mine2
            }
        };
        adapter1.SelectCommand.Parameters.AddRange(parameters);

        var data1 = new DataTable();
        adapter.Fill(data1);
        dataGridView1.DataSource = data1
    }        
}