I have one NumericUpDown1 control
if i select 5 in numeric up down control.the i am calling that value like this:
NumericUpDown1.Value
that return value 5 like integer instead of getting 5.
i want to get that value in time format
I if i select 5.that should return 00:05:00..
how i can convert numeric up down value to times..
in my data base i want to store that value the data type time(7).I tryed something like this:
Dim value As TimeSpan = Convert.ToDecimal(NumericUpDown1.Value)
but that is getting error
You are using TimeSpan wrongly, better rely on Date:
Dim value As Date = New Date(Now.Year, Now.Month, Now.Day, 0, NumericUpDown1.Value, 0)
You can convert this variable into a string with the format you want by doing:
Dim valueAsString As String = value.ToString("HH:mm:ss")
This is the right way to use TimeSpan:
Dim value As TimeSpan = New TimeSpan(0, NumericUpDown1.Value, 0)
But I do recommend the Date alternative above. Use TimeSpan just for measuring intervals (between Date type variables) and better store date/time-related information as Date, which is easier to deal with.
Related
My Code:
listDates = (From row In ds.Tables(0) Select row.Field(Of Date)("Check In")).ToList
arrDates = listDates.ToArray
For a = 0 To arrDates.Length - 1
arrDatesStr(a) = (arrDates(a)).ToString
Next
I am making an analytics form to find the most popular month for a hotel:
listDates is a list that stores all of the dates from the database
arrDates is the conversion of listDates to an array
arrDatesStr is the array I need to fill with the date values but as strings, so i can substring the month
I have checked the values in listDates and arrDates and they conversion is successful, but when I try to convert it to string it says
"System.NullReferenceException: 'Object reference not set to an instance of an object.'"
How do I convert arrDates to a string and input those values into arrDatesStr?
arrDatesStr(a) has not been initialized.
You can add something like dim arrDatesStr(arrDates.length-1) before you use arrDatesStr. Better yet, don't use arrDates at all:
For a = 0 To listDates.Length - 1
arrDatesStr(a) = listDates(a).ToString
Next
If you use date.month instead of substring to get the month, you won't have to worry about whether it's a 1 or 2 digit month, and you won't have to convert it to string.
m = listDates(a).Month
Unless you have a good reason not to, you should let the conversion create the array for you:
Dim dateStrings = Array.ConvertAll(dates, Function(dt) dt.ToString())
or:
Dim dateStrings = dates.Select(Function(dt) dt.ToString()).ToArray()
That will create a String array of the appropriate length, containing the appropriate data.
Note that the first option requires an array but the second option will work on any IEnumerable(Of Date), which includes the List(Of Date) or even the original query.
I AM FACING ONE PROBLEM.
I AM USING BELOW METHOD FOR MAKING STRING VALUE TO DATE.
string values is like this ="01/12/2002" like "dd/MM/YYYY"
My problem is that.
two string values
->1)01/01/2025
->2)1/1/2025
i am getting the Value like above 1 or 2
Dim d As Date = DateTime.ParseExact(dumm, "dd/MM/yyyy", Nothing)
if 1 comes nothing will happen but
if i get 2 i am facing error like String was not recognized as a valid DateTime.
As per my Analysts what i understood is date should be 2 digits Remaining all are two digits other wise giving the error.
but some times i am getting single digits from the excel to vb.net
how can i solve this issue...
Dim dumm As String = DtSet3.Tables(0).Rows(k + 0).Item(3).ToString
Dim d As Date = DateTime.ParseExact(dumm, "d/M/yyyy", Nothing)
i put the break point on dumm ok dumm vlaues= "1/2/2026 12:00:00 Am"
Error...............
now
Dim dumm As String = DtSet3.Tables(0).Rows(k + 0).Item(3).ToString
Dim d As Date = DateTime.ParseExact("01/02/2026", "dd/MM/yyyy", Nothing)
Working Fine.......
Use the date format string "d/M/yyyy h:m:s tt". This will handle both cases i.e. with and without leading zero for the day and month. Additionally, since your actual variable has a time component in addition to the date, you need to add the format string for parsing time as well.
However, I would advise you to use TryParseExact, which will return boolean values based on success or failure of the parse rather than throwing exceptions.
Demo for using TryParseExact along with appropriate format string.
I want to convert str into DateTime.
For that which option should I used in VB.NET? And Why?
I tend to do it like this:
Dates "disguised" as Object
If I know the object is a datetime I use CType:
Dim table As New DataTable("Table")
table.Columns.Add("DATETIME_COLUMN", GetType(DateTime))
table.Rows.Add(Date.Now)
table.AcceptChanges()
Dim d As DateTime = CType(table.Rows(0).Item("DATETIME_COLUMN"), DateTime)
Strings
When dealing with strings I use DateTime.Parse. Notice that you can pass a cultureinfo.
Dim d As DateTime = DateTime.Parse("10.02.2014", New System.Globalization.CultureInfo("nb-NO"))
Unknown/mixed types
Finally, if I cannot be sure of the datatype, I use Convert.ToDateTime:
Dim d As DateTime = Convert.ToDateTime(obj, New System.Globalization.CultureInfo("nb-NO"))
CType & CDate are VB.NET functions that have defined functionality.
Ctype('01/01/2014',DateTime)
DateTime.Parse is a BCL (Base class library) method that has defined
functionality.
Dim value As String = "2000-02-02"
Dim dt As DateTime = DateTime.Parse(value)
As long as your string is in the right date format, you can just use CDate() function. This is the fastest and easiest way since you only have to type 7 characters excluding the string to be converted :) In terms of efficiency and speed, doesn't really make a difference.
Alright, so I'm not exactly very oriented when it comes to functions available in VB.
I have a string containing the current date and time and need to convert it to a integer so i can compare the time.
Dim my_str as String = "201308281110"
Dim my_int as Integer = Convert.ToInt32(my_str)
I cant do that with this string apparently. Because I think it is too long for the 32-bit integer. All the other convertions I have tried also fails. That including "ToInt64", "Int", "CInt"... So, any idea how to convert this longer string to an integer?
Why don't you just simply use Date? You can compare Dates with each other, so there's no need to use an integer for comparing.
Dim my_date as Date = DateTime.ParseExact(my_str, "yyyyMMddhhmm", System.Globalization.CultureInfo.InvariantCulture)
Normally I wouldn't do this. Several correct answers have already been given, but since you are still learning VB.NET, I feel like a more thorough answer would be helpful to you. So my answer will repeat some of what others have already said.
The Int64 and Decimal types are indeed big enough to to hold a number like that. I suspect that the reason why Convert.ToInt64 wasn't working for you is because you were trying to store the results in an Integer variable, like this:
Dim my_str as String = "201308281110"
Dim my_int as Integer = Convert.ToInt64(my_str) ' Throws an OverflowException
The reason that fails is not because ToInt64 doesn't work. That part of the statement is actually working fine. The part that's failing is where you are assigning the my_int variable to the value. my_int is declared as an Integer. The Integer type in VB.NET is actually just a pseudonym for Int32. In other words, it's actually the same thing as this:
Dim my_str as String = "201308281110"
Dim my_int as Int32 = Convert.ToInt64(my_str) ' Throws an OverflowException, just like the above example
To correct the problem, you need to change the type of the my_int variable to Int64 so that it will be big enough to hold the value being returned from the ToInt64 function.
Dim my_str as String = "201308281110"
Dim my_int as Int64 = Convert.ToInt64(my_str) ' Works
In VB.NET, Long is the pseudonym for Int64, so in most cases, that's what you should use. If you are going to use Long, however, using the ToInt64 method is a little ugly. It would be easier to read to just use Long on both sides of the assignment, like this:
Dim my_str as String = "201308281110"
Dim my_int as Long = Long.Parse(my_str) ' Works, just like above
That also makes the code marginally safer because it will still work even if the size of Long changes in the future (however unlikely that may be).
The Decimal type would also be large enough to hold the value, but it would be less efficient than using Long, so I wouldn't recommend it.
This begs the question, however, "Why are you doing this?" If you need to compare the value to another Long variable, it would make sense to do that, but then how did you get that other Long value? If you are converting both Long values from strings, then it doesn't make sense to do that. The string is already formatted in a way where it can be easily compared with other strings of the same format. For instance:
Dim dateTime1 As String = "201308281110"
Dim dateTime2 As String = "201308281850"
If dateTime1 > dateTime2 Then
' Doesn't get here
End If
If dateTime1 < dateTime2 Then
' Get's here
End If
If dateTime1 = dateTime2 Then
' Doesn't get here
End If
If, however, you need to parse the value to read its individual parts (e.g. date, time, year, month, hour), it makes more sense to convert the value to a DateTime value. Or, if you need to compare the string value to another value which is already stored in a DateTime variable, then, in that case, it also makes sense to convert the string to a DateTime value. In VB.NET, the pseudonym for DateTime is simply Date, so in most cases, you should just use that, like this:
Dim my_str as String = "201308281110"
Dim my_date as Date = Date.ParseExact(my_str, "yyyyMMddHHmm", System.Globalization.CultureInfo.InvariantCulture)
If my_date > Date.Now Then
' Do stuff
End If
But Long.Parse works as well as Convert.ToInt64 since it doesn't overflow(Int32.MaxValue is 2147483647):
Dim myLong1 = Long.Parse("201308281110")
Dim myLong2 = System.Convert.ToInt64("201308281110")
Demo
Note that Long is the same as Int64.
I am saving my numericupddown value like this into database
Dim value As Date = New Date(Now.Year, Now.Month, Now.Day, 0, NumericUpDown1.Value, 0)
Dim valueAsString As String = value.ToString("HH:mm:ss")
..it will save data like 00:05:00.
I want to fetch corresponding data to my numeric updown control.
I am fetching data using my data reader.then i try to give code like this:
NumericUpDown1.Value = Convert.ToDecimal(dr("Timeinterval")).ToString
But showing
error:Unable to cast object of type `System.TimeSpan` to type `System.IConvertible`.
How can I show corresponding data to my numericupdown control?
You are trying to convert 00:05:00 to a decimal, which obviously is wrong. Before saving to database, you changed the value in your updown control to HH:mm:ss format. Now you need to write custom logic to convert 00:05:00 to number like ((HH * 60) + mm + (ss / 60)) before you would be able to convert it back to Decimal.