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.
Related
Hi Guys
Can anyone help me out with this problem i have a list of object that is formatted in the image attached above and i have to get the IDNO, Affected Id and the date values
Since deserialization will return anonymous type(in your case), you have two options: Either deserialize it to a strong type (by defining a type) or else fetch the value using Reflection since types and properties are not known.
In your case you can get the value through reflection like this:-
Dim _data As List(Of Object) = ...
Dim firstObject = _data.FirstOrDefault()
Dim type As Type = firstObject.GetType()
Dim idmoValue = type.GetProperty("IDMO").GetValue(firstObject)
Sample Fiddle.
I have a data grid using dynamic data. I 'enable' dynamic data on the page_init event for the page containing the data grid. I would like to be able to set the type of the dynamic data at run time. I have the name of the class to set, as a string. I can't quite figure out how to do this.
I set the dynamic data like this:
Dim myGrid As GridView = DirectCast(retrieveGrid.FindControl("gridResults"), GridView)
myGrid.EnableDynamicData(GetType(*MyEntityNameAsAString*)
Obviously this does not work because I cannot provide my entity name a s a string. How can I convert the string to the entity type? I tried:
Type.GetType(entityname)
And
Type.GetType(AssemblyName.entityname)
And neither seems to work. That is, I can't get the type with either of these statements.
OK, solved it like this... I created a function to get the entity object from the object name:
Public Function GetEntity(ByVal entityName As String) As Object
'Get the assembly
Dim assem As Assembly = Nothing
assem = Assembly.LoadFrom(AppDomain.CurrentDomain.BaseDirectory & "/bin/AsbestosEntities.dll")
'Get all classes in the assembly
Dim AllEntities As Type() = assem.GetTypes()
Return AllEntities.FirstOrDefault(Function(e) e.FullName = entityName)
End Function
Then set the grid enable dynamic data based on the result of the function:
Dim EntityType As Type = GetEntity(general_retrieve.gr_entity_set_name)
myGrid.EnableDynamicData(EntityType)
To preface this, I've looked through several of the postings containing listviews and nothing really is comparing to what I'm trying to do.
I'm trying to take values determined through a loop that has several If Statements similar to what follows:
If Convert.ToInt32(GetData(ds.Tables("HRIS").Rows(i), "ABS_CO_RULE_DAYS", DefaultValue)) > 0 Or _
Convert.ToInt32(GetData(ds.Tables("HRIS").Rows(i), "ABS_CO_RULE_HRS", DefaultValue)) > 0 Or _
Convert.ToInt32(GetData(ds.Tables("HRIS").Rows(i), "ABS_CO_RULE_MINS", DefaultValue)) > 0 Then
msChargeDays = GetData(ds.Tables("HRIS").Rows(i), "ABS_CO_RULE_DAYS", DefaultValue)
msChargeHours = GetData(ds.Tables("HRIS").Rows(i), "ABS_CO_RULE_HRS", DefaultValue)
msChargeMins = GetData(ds.Tables("HRIS").Rows(i), "ABS_CO_RULE_MINS", DefaultValue)
msHowPaid = "CR DAYS"
AbsenceLine() 'calls sub
End If
This block of code returns valid results from the dataset that it calls from. Now in the following code block, I am trying to assimilate values that are determined by the main code block which is about 40 if statements similar in structure to the block above, all contained within a For loop.
In the following code block I am trying to insert an object of ListViewItem type into the ListView. This is where I'm getting my error denoted by comment string following it. The function that fills the ListViewItem is at the bottom, all of the variables returned are all class variables and return valid values to the ListViewItem. I have double checked this via the debugger.
Private Sub AbsenceLine()
Dim sTypeReason As String
If msType = "" Then
sTypeReason = Left(msReason, 25)
Else
sTypeReason = msType & "--" & msReason
End If
Dim item As ListViewItem
item = New ListViewItem(ListViewItemType.DataItem)
item.DataItem = FillListView(sTypeReason)
absence_lv.Items.Add(item) 'this line here is what is givine me issues
End Sub
Private Function FillListView(typeReason As String) As IEnumerable(Of String)
Return {msDate, msVoid, msCont, msDays, msHours, msMinutes, typeReason, msChargeDays, msChargeHours,
msChargeMins, msHowPaid} 'all values returned are of String type
End Function
Now with the background:
Am I completely off base with what I'm trying to do?
Is there an easier way to do this with a gridview instead?
I think you're misusing the DataItem property of the ListViewItem class. That's really used to get the underlying object that the ListViewItem represents when the ListView itself is bound.
Since your FillListView function is returning an IEnumerable(Of String), you can just set the ListView's DataSource property to the function call.
absence_lv.Datasource = FillListView(sTypeReason)
absence_lv.Databind()
As you can see, there is no need to manually add each item.
I am using DataTable.Select() method to filer based on some conditions.
dtRows = m_dtTable.Select(String.Format("IdentifierID={0}", dtRow
("QuestionID").ToString))
I used the similar way to sort the data in different places . But only one place i am getting error.
Can any help me to find why this exception is occurs? Also help me to know why there is no exception in other places ? The values of datatable is filled from a stored procedure.
Min (2) must be less than or equal to max (-1) in a Range object. is exception I am getting.
EDIT -- After the First Answer --
I am getting exception not every time, but only some time that I cannot identify the scenario. :(
ADDED -- After the First Answer --
Thanks for the solution. :)
Note : m_DependantQuestionsDataTable and m_dtTable are same by its schema.
colIdentifierID.DataType = Type.GetType("System.String")
colIdentifierID.ColumnName = "IdentifierID"
This is the type of particular column. There is also another column which is also similar type and there is no error occurs when I use it with the similar method.
colQuestionID.DataType = Type.GetType("System.String")
colQuestionID.ColumnName = "QuestionID" is the column and I am using like this. ' Dim strFilterExpression As String = "questionID={0}" m_DependantQuestionsDataTable.Select(String.Format(strFilterExpression, dRow("QuestionID")))'
Here there is no exception or error is occurring . So if I am choosing your solution I need to change the Filter Expression by adding ' in all place in my solution where I am using Filter Method.
You don't specify the data type of the column you're filtering on and if it's a string then you'll need to add single quotes around the parameter in your filter expression:
dtRows = m_dtTable.Select(String.Format("IdentifierID='{0}'", dtRow("QuestionID").ToString()))
alternatively, if you want to sort+ filter via the DGV, without need to repopulate the DT and DGV, you can use .Sort and .RowFilter of the DataView
http://msdn.microsoft.com/en-ca/library/system.data.dataview.rowfilter.aspx
Private _DS As New DataSet
Private _DT As New DataTable
Private _DV As New DataView
Private _DGV As New DataGridView
Private _isFiltering As Boolean = False
Private Sub filterView()
If _isFiltering Then Return
_isFiltering = True
Dim _SF As String = "price ASC"
'Dim _RF As String = tableStructure.Columns(0).Name & " < 20" ' just an example
Dim _RF As String = "price < 20"
_DGV.ClearSelection()
_DT.DefaultView.Sort = _SF
_DT.DefaultView.RowFilter = _RF
_isFiltering = False
End Sub
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.