Reading an SQLite DateTime value from database and assigning it to a C# string variable

Question

I have a database with a datatable which includes a DateTime column among other things. When using SQL server, I could read the DateTime value from the database using the following code:

    SqlCommand getdate = new SqlCommand("SELECT * FROM EMPinfo WHERE id = @employeeId", connect);
                getdate.Parameters.AddWithValue("@employeeId", listViewEmployee.SelectedItems[0].SubItems[2].Text);
                getdate.Connection = connect;
                connect.Open();
                SqlDataReader readList = getdate.ExecuteReader(CommandBehavior.CloseConnection);
                while (readList.Read())
                {
                    lblEmpDob.Text = ((DateTime)readList["dob"]).ToString("d");
                }

After changing the code to run with SQLite:

    SQLiteConnection connect = new SQLiteConnection(@"Data Source=quotevodata.db;");
                SQLiteCommand getlistname = new SQLiteCommand("SELECT * FROM EMPinfo WHERE id = @employeeId", connect);
                getlistname.Parameters.AddWithValue("@employeeId", listViewEmployee.SelectedItems[0].SubItems[2].Text);
                getlistname.Connection = connect;
                connect.Open();
                SQLiteDataReader readList = getlistname.ExecuteReader(CommandBehavior.CloseConnection);
                while (readList.Read())
                {
                     lblEmpDob.Text = ((DateTime)readList["dob"]).ToString("d");

                }

I keep getting the following error: "String was not recognized as a valid datetime."

I've tried different combinations and declaration of variables but it's not working out. What is the correct configuration to read DateTime values out of an SQLite database?

Answer 1

SQLite does not have a built-in DateTime object, but rather stores them as Text, Real, or Int values.

From your error, you can infer that it's outputting as text; Which according to SQLite documentation should be in the format of "YYYY-MM-DD HH:MM:SS.SSS"

There are various ways you could parse this to a DateTime object, but I'll use RegEx:

public static DateTime ConvertToDateTime(string str)
{
    string pattern = @"(\d{4})-(\d{2})-(\d{2}) (\d{2}):(\d{2}):(\d{2})\.(\d{3})";
    if (Regex.IsMatch(str, pattern))
    {
        Match match = Regex.Match(str, pattern);
        int year = Convert.ToInt32(match.Groups[1].Value);
        int month = Convert.ToInt32(match.Groups[2].Value);
        int day = Convert.ToInt32(match.Groups[3].Value);
        int hour = Convert.ToInt32(match.Groups[4].Value);
        int minute = Convert.ToInt32(match.Groups[5].Value);
        int second = Convert.ToInt32(match.Groups[6].Value);
        int millisecond = Convert.ToInt32(match.Groups[7].Value);
        return new DateTime(year, month, day, hour, minute, second, millisecond);
    }
    else
    {
        throw new Exception("Unable to parse.");
    }
}

docs: http://www.sqlite.org/datatype3.html

Answer 2

Thanks for the answers, I finally got it to work by changing the INSERT statement to SQLite format as suggested:

    string empDob = dateDOB.Value.ToString("yyyy-MM-dd");
    //I then inserted this string into the database with the column configured as a "DATE" datatype.

After that, I used the following statements to read and format the date to usable string and it worked beautifully:

    DateTime dateOfBirthEmp = DateTime.Parse(readList["dob"].ToString());

    lblEmpDob.Text = dateOfBirthEmp.ToString("d");

I really appreciate the help.

Answer 3

Why do you convert 2 times?

If you have a Date column in SQLite the provider can manged that for you. You can direct insert as DateTime and read as DateTime.

Answer 4

It's feels a bit hacky but this is the only solution I was able to come up with. It just creates a new column, copies all the values in DateTime format to the new column and deletes the old time string column.

DataTable dt = GetDataTable();
string tc = "TimeColumnName";

dt.Constraints.Clear();
int ordinal = dt.Columns[tc].Ordinal;
dt.Columns[tc].ColumnName = "TSOLD";
dt.Columns.Add(tc, typeof(DateTime));
foreach (DataRow row in dt.Rows) row[tc] = Convert.ToDateTime(row["TSOLD"]);
// remove "OLD" column
dt.Columns.Remove("TSOLD");
dt.Columns[tc].SetOrdinal(ordinal);
dt.Constraints.Add(new UniqueConstraint(dt.Columns[tc]));