I am trying to retrieve a value from a GridView and save it as a Date variable, using the following code:
Dim invoice_date As Date = Convert.ToDateTime((TryCast(row.Cells(2).Controls(0), TextBox)).Text)
I am getting an error:
System.Web.UI.WebControls.TextBox) returned Nothing.
From what I have read, if the TryCast fails, it will return a value of nothing.
I have a similar command for an Integer, which works fine on another column.
Dim order_value As Integer = Convert.ToInt32((TryCast(row.Cells(3).Controls(0), TextBox)).Text)
Can somebody please help with the correct syntax to work with a Date value?
You are right that TryCast returns Nothing if it cannot cast to the target type. So, the problem that you have is most likely that row.Cells(2).Controls(0) is not a TextBox. To debug this, split the line:
Dim invoice_date As Date = Convert.ToDateTime((TryCast(row.Cells(2).Controls(0), TextBox)).Text)
like this:
Dim textbox As TextBox = TryCast(row.Cells(2).Controls(0), TextBox)
Dim invoice_date As Date = Convert.ToDateTime(textbox.Text)
and look at the value of textbox.
Try and use DirectCast() and see if that works.
Related
I am trying to convert a string to textbox, but I am getting an error that it cannot convert to integer?!
I have the following code:
Dim curr As String
curr = "Detail_0107"
Dim NEWTEXT As TextBox = TryCast(Me.Controls(curr), TextBox)
NEWTEXT.Text = "test"
On the TryCast, I get the following error:
Conversion from string "Detail_0107" to type 'Integer' is not valid
Detail_0107 is a textbox on my form. Can I do this?
Thanks
Your problem seems to be that you're setting Detail_0107 as a string. If you want to set the text of Detail_0107, all you need to do is the following:
Detail_0107.Text = "test"
As you said Detail_0107 is already a textbox on your form, there shoud already be an object for it.
Try using Me.Controls.Find(curr) instead. Additionally, every control has a .Text property. It's part of the base Control type, and therefore you have no need to cast to TextBox. If you're very sure the Detail_0107 control does exist in that collection, you can get the code down to just this:
Me.Controls.Find("Detail_0107").Text = "test"
I cannot find a complete example. Found tons on grid and combobox, but not textbox. This test is to lookup a “PhoneTypeName” from a UserPhoneType table with TypeCode = “0” and assign that first value to a asp.net textbox.
Currently, I am getting “Object reference not set to an instance of an object” when setting the text box to "phonetype.FirstOrDefault.PhoneTypeName.ToString"
Using dbContext As New EntitiesModel()
Dim phonetype As IEnumerable(Of User_PhoneType) = dbContext.User_PhoneTypes.Where(Function(c) c.PhoneTypeCode = "O")
mytextbox.Text = phonetype.FirstOrDefault.PhoneTypeName.ToString
End Using
----EDIT----
I changed as suggested. I ALSO successfully bound the entire list of PhoneTypes to a droplist control...to confirm the data is accessible. It must be the way I am going about querying the table for a single record here.
I get the same error, but at "Dim type = phonetype.First..."
The record is in the table, but it does not appear to be extracted with my code.
Dim phonetype As IEnumerable(Of User_PhoneType) = dbContext1.User_PhoneTypes.Where(Function(c) c.PhoneTypeCode = "M")
Dim type = phonetype.FirstOrDefault
If Object.ReferenceEquals(type, Nothing) = False And Object.ReferenceEquals(type.PhoneTypeName, Nothing) = False Then
mytextbox.Text = type.PhoneTypeName.ToString
End If
In general there are the following two possible reasons for getting this exception:
1) The phonetype list is empty and the FirstOrDefault method is returning a Nothing value.
2) The PhoneTypeName property of the first element of the phonetype list has a Nothing value.
In order to make sure that you will not get the Object reference not set to an instance of an object exception I suggest you add a check for Nothing before setting the TextBox value. It could be similar to the one below:
Dim type = phonetype.FirstOrDefault
If Object.ReferenceEquals(type, Nothing) = False And Object.ReferenceEquals(type.PhoneTypeName, Nothing) = False Then
mytextbox.Text = type.PhoneTypeName.ToString
End If
Fixed it.
I was able to view the SQL string being generated by using this:
mytextbox.text = phonetype.tostring
I saw that the SQL contained "NULL= 'O'"
I did it like the example?!? However, when I added .ToString to the field being queried, it worked.
So the final looks like this:
Using dbContext As New EntitiesModel()
Dim phonetype As IEnumerable(Of User_PhoneType) = dbContext.User_PhoneTypes.Where(Function(c) c.PhoneTypeCode.**ToString** = "O")
mytextbox.Text = phonetype.FirstOrDefault.PhoneTypeName.ToString
End Using
BTW, Dimitar point to check for null first is good advice (+1). The value was nothing as he said.
I have a FormView where I pull data from one table (MS Access), and then insert it (plus more data) into another table. I'm having issues with the dates.
The first table has two date fields: date_submitted and date_updated. In some records, date_updated is blank. This causes me to get a data mismatch error when attempting to insert into the second table.
It might be because I'm databinding the date_updated field from the first table into a HiddenField on the FormView. It then takes the value from the HiddenField and attempts to insert it into the second table:
Dim hfDateRequestUpdated As HiddenField = FormView1.FindControl("hfDateRequestUpdated")
myDateRequestUpdated = hfDateRequestUpdated.Value
'... It then attempts to insert myDateRequestUpdated into the database.
It works when there is a value there, but apparently you can't insert nothing into a date/time field in Access. I suppose I could make a second insert statement that does not insert into date_updated (to use when there is no value indate_updated), but is that the only way to do it? Seems like there should be an easier/less redundant way.
EDIT:
Okay. So I've tried inserting SqlDateTime.Null, Nothing, and DBNull.Value. SqlDateTime.Null results in the value 1/1/1900 being inserted into the database. "Nothing" causes it to insert 1/1/2001. And if I try to use DBNull.Value, it tells me that it cannot be converted to a string, so maybe I didn't do something quite right there. At any rate, I was hoping that if there was nothing to insert that the field in Access would remain blank, but it seems that it has to fill it with something...
EDIT:
I got DBNull.Value to work, and it does insert a completely blank value. So this is my final working code:
Dim hfDateRequestUpdated As HiddenField = FormView1.FindControl("hfDateRequestUpdated")
Dim myDateRequestUpdated = Nothing
If hfDateRequestUpdated.Value = Nothing Then
myDateRequestUpdated = DBNull.Value
Else
myDateRequestUpdated = DateTime.Parse(hfDateRequestUpdated.Value)
End If
Thanks everyone!
Sara, have you tried casting the date/time before you update it? The data mismatch error likely comes from the fact that the hfDateRequestUpdated.Value you're trying to insert into the database doesn't match the column type.
Try stepping through your code and seeing what the type of that value is. If you find that it's a string (which it seems it might be, since it's coming from a field on a form), then you will need a check first to see if that field is the empty string (VBNullString). If so, you will want to change the value you're inserting into the database to DBNull, which you can get in VB.Net using DBNull.Value.
We can't see your code, so we don't know exactly how you get the value into the database, but it would look something like this
If theDateValueBeingInserted is Nothing Then
theDateValueBeingInserted = DBNull.Value
EndIf
Keep in mind that the above test only works if the value you get from the HiddenField is a string, which I believe it is according to the documentation. That's probably where all this trouble you're having is coming from. You're implicitly converting your date/time values to a string (which is easy), but implicitly converting them back isn't so easy, especially if the initial value was a DBNull
aside
I think what Marshall was trying to suggest was the equivalent of the above code, but in a shortcut expression called the 'ternary operator', which looks like this in VB.Net:
newValue = IF(oldValue is Nothing ? DBNull.Value : oldValue)
I wouldn't recommend it though, since it's confusing to new programmers, and the syntax changed in 2008 from IFF(condition ? trueResult : falseResult)
Your code
Dim myDateRequestUpdated As DateTime
myDateRequestUpdated = DateTime.Parse(hfDateRequestUpdated.Value) : DBNull.Value()
has a couple of problems:
When you declare myDateRequestUpdated to be DateTime, you can't put a DbNull.Value in it.
I'm not sure you need the () for DbNull.Value: it's a property, not a method (I don't know enough VB to say for sure)
VB doesn't know that : operator
What you probably want is a Nullable(Of DateTime) to store a DateTime value that can also be missing.
Then use something like this to store the value:
myDateRequestUpdated = If(String.IsNullOrWhiteSpace(hfDateRequestUpdated.Value),
Nothing, DateTime.Parse(hfDateRequestUpdated.Value))
If hfDateRequestUpdated.Value is empty, then use Nothing as the result; else parse the value as date (which might fail if it is not a valid date!).
Try this:
Protected Sub Button2_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button2.Click
Dim str As String
If TextBox1.Text.Length <> 0 Then
str = "'" & TextBox1.Text & "'"
Else
str = "NULL"
End If
sql = "insert into test(test1) values(" & str & ")"
dsave_sql(sql)
End Sub
Function save_sql(ByVal strsql As String, Optional ByVal msg As String = "Record Saved Sucessfully") As String
Dim sqlcon As New SqlConnection(strConn)
Dim comm As New SqlCommand(strsql, sqlcon)
Dim i As Integer
Try
sqlcon.Open()
i = CType(comm.ExecuteScalar(), Integer)
save_sql = msg
Catch ex As Exception
save_sql = ex.Message
End Try
sqlcon.Close()
Return i
End Function
Hello
I'm trying to update a ms access database. I've got a gridview with a date that i use:
Dim tBox As TextBox = CType(gridStaff.Rows(e.RowIndex).FindControl("sDate"), TextBox)
I then want to take the value from this textbox and assign it to a date variable.
Dim test As Date = CDate(tBox.Text)
The problem I have is that now when I put test variable into my sql update query it stores the date in this format. mm/dd/yyyy instead of the dd/mm/yyyy format I want.
Ive tried different ways to format it I read online but to no success yet. Any advice would be great!
Thanks
Is your problem the conversion from tBox.Text to Date, or is it at the sql update query level? -- You should probably give the sql statement a parameter with a strict type. Converting from tBox.Text into test should probably be done in a Culture aware manner:
'String to convert and target date:
Dim dateString As String = "02/15/2011"
Dim d As Date
' Specify English/US culture when converting string:
Dim cul As Globalization.CultureInfo = Globalization.CultureInfo.GetCultureInfo("en-US")
d = Date.Parse(dateString, cul)
You could also rely on the default culture and simply let Date.Parse do the job without specifying the culture.
try using
Dim test As Date = DateTime.ParseExact(tBox.Text, "d/M/yyyy", CultureInfo.InvariantCulture)
or if your System is set up right and CultureInfo.CurrentCulture has the right date format,
Dim test As Date = DateTime.Parse(tBox.Text, CultureInfo.CurrentCulture )
instead of CDate()
I'm trying to reference a public property from a string. How can this be done in vb.net?
I have the text value of "FirstName" stored in strucParam(i).TxtPropertyName.
This is what I'm currently doing:
Dim tmpValue As String
Dim ucAppName As UserControl_appName = CType(Parent.FindControl(strucParam(i).ParentFindControl), UserControl_appName)
tmpValue = ucAppName.FirstName.Text
How can I use the value in strucParam(i).TxtPropertyName so that I can remove ".FirstName" from my code? Thanks!
This is basically a duplicate of this question, but I'll answer it for you since you're a VB user and probably didn't consider C# in your searches.
Suppose you have an object of any type stored in a variable called objObject, and the name of the property stored in a variable called strPropertyName. You do the following:
tmpValue = objObject.GetType().GetProperty(strPropertyName).GetValue(objObject, Nothing)
As a final note: please, please consider dropping pseudo-Hungarian notation. It's of no value when working with a statically typed language like VB.NET.
Edit:
The FirstName property is in reality a text box. So don't I need to somehow reference .Text in the code?
tmpFirstName = ucAppName.GetType().GetProperty(strucParam(i).PropertyName).GetValue(objAppNav, Nothing)
Try this:
Dim textBox as TextBox
Dim tmpValue as String
textBox = CType(ucAppName.GetType().GetProperty(strucParam(1).PropertyName).GetValue(objAppNav, Nothing), TextBox)
tmpValue = textBox.Text
Basically, you have to cast the value of the property to a TextBox type, then grab the Text property from it.