I have the following string expression:
str="1+2+3+4"
Now from this string I want the value of number (10). How can I get this value from this expression?
For that to work, you'd have to parse all the numbers, something like this
Dim str As String= "1+2+3+4"
Dim numbers() As String = str.Split('+')
Dim result As Integer = 0
For Each number As String In numbers
result += Integer.Parse(number)
Next
Here is an alternative solution that uses Linq. This solution excludes nothing it can not parse...
YOURSTRING.Split("+").ToList.Where(Function(sr) Not String.IsNullOrEmpty(sr) AndAlso Integer.TryParse(sr, New Integer)).Sum(Function(s As String) Integer.Parse(s))
Example Output
1+2+3+4 = 10
1+2+3+4++12+1 = 23 (Notice the typo (4++12), it still works even it there's a mistake)
I have tried several casts and can't get this to work.
Here is what I am trying to convert into a linq query in vb.net:
The Ids are of type int
Dim listOfProductIds As New List(Of String)
For Each s In Products
listOfProductIds.Add(s.Id)
Next
This is what isn't working when I expect it to:
Dim listOfProductIds As List(Of String) = (From s In Products
Select s.Id.ToString()).ToList()
Maybe I'm not following what you are trying to do but converting int to a string is straight forward.
Dim listOfProductIds As New List(Of String)
For Each s In Products
listOfProductIds.Add(s.Id.ToString())
Next
You have to convert the value like this because we can't project the ToString() function to a LINQ variable.
Dim _ids = (From p In products Select Convert.ToString(p.Id)).ToList
i have a database in one field like below 222-225. I try to make split to read that value for my function. Just simple function a=225 b=222 then total=(a-b)+1. here my code
Dgv.CellClick
'Dim x As Boolean
Dim a As Double
Dim total As Double
a = CDbl(Dgv.Item(8, Dgv.CurrentRow.Index).Value)
Split(a, "-")
total = (a) - (a)
Dgv.Item(9, Dgv.CurrentRow.Index).Value = total
My problem is this doesn't work. I can't get the value that I split. Any idea how to solve this problem?
note: I use VB.NET 2005
If you want total=(a-b)+1 .. That should be
dim b = a.Split("-")
total = val(b(1)) - val(b(2)) + 1
may be this can help. try this...
Dim a As String
a = ""
Dim x As String
Dim total As Double
a = Dgv.Item(8, Dgv.CurrentRow.Index).Value.ToString
Dim ary() As String
x = a
ary = x.Split("-")
total = CInt(ary(1)) - CInt(ary(0))
Dgv.Item(9, Dgv.CurrentRow.Index).Value = total
Like others have said, Split() returns a String array, like this:
Dim SplitValue() As String = Split(a, "-")
total = (CType(SplitValue(1), Double) - CType(SplitValue(0), Double)) + 1
If I read your question correctly, the value you're looking for is 222-225, and that value is located in the specified cell of Dgv (which I'm guessing is a DataGridView). If my understanding is correct, there are a couple of things going on.
First, I'm not sure why you're trying to convert that value to a double with the following line of code:
a = CDbl(Dgv.Item(8, Dgv.CurrentRow.Index).Value)
The Item property of a DataGridView holds a DataGridViewCell, and the Value property of the DataGridViewCell returns an Object. Trying to convert 222-225 to a double will, I believe, fail (though since this is VB.NET, it's possible it won't depending on the options you set - I'm not as familiar with VB.NET as I am with C#).
Even if it does successfully work (I'm not sure what the output would be), Split expects a string. I would change that line of code to the following:
a = Dgv.Item(8, Dgv.CurrentRow.Index).Value.ToString()
Now you have a string that you can use Split on. The Split you have in your posted code appears to be the Visual Basic (pre-.NET) Split method Split Function (Visual Basic). As others have mentioned, Split returns an array of strings based on the delimiter. In your code, you don't assign the result of Split to anything, so you have no way to get the values.
I would recommend using the .NET version of Split (String.Split Method) - there are several ways you can call String.Split, but for purposes of your code I'd use it like this:
Dim splits As String() = a.Split(New Char() { "-" })
Where a is the string value from the selected DataGridViewCell above. This will give you a 2-element array:
splits(0) = "222"
splits(1) = "225"
The final part is your formula. Since you have strings, you'll need to convert them to a numeric data type:
total = (CDbl(splits(1)) - CDbl(splits(0))) + 1
Which becomes (225 - 222) + 1 = 4.
Putting it altogether it would look something like this:
Dim a As String
Dim total As Double
Dim splits() As String
a = Dgv.Item(8, Dgv.CurrentRow.Index).Value.ToString()
splits = a.Split(New Char() { "-" })
total = (CDbl(splits(1)) - CDbl(splits(0))) + 1
Dgv.Item(9, Dgv.CurrentRow.Index).Value = total
Split returns an array. something like this. VB.Net is not my primary language but this should help.
dim arr = a.Split(New Char (){"-"})
total = ctype(arr(0), double) - ctype(arr(1),double)
Try this:
Dim aux() As String = a.Split("-"c)
total = CDbl(aux(0)) - CDbl(aux(1)) + 1
Dim a As string
Dim x As String
Dim total As Double
a = Dgv.Item(8, Dgv.CurrentRow.Index).Value
Dim ary() As String
x = a
ary() = x.Split("-")
total = CInt(ary(1)) - CInt(ary(0))
Dgv.Item(9, Dgv.CurrentRow.Index).Value = total
i have the following code which will get the max and min values from a list of type double
Dim sprices As List(Of Double) = grp.ProductGroups.AsEnumerable().[Select](Function(sm) sm.Field(Of Double)("sprice")).Distinct().ToList()
Dim min As Integer = sprices.Min()
Dim max As Integer = sprices.Max()
how ever in the first line i get the exception "Cannot cast DBNull.Value to type 'System.Double'. Please use a nullable type."
how can i avoid this or not add the DBNulls to the list?
One way is to use a nullable Double, which can be expressed as Double?:
Dim sprices As List(Of Double?) = grp.ProductGroups.AsEnumerable().[Select](Function(sm) sm.Field(Of Double?)("sprice")).Distinct().ToList()
I want to get value from datatable and then store it to the string() arraylist. datatable contain 3 column (columnA | columnB | columnC). I want to get all value from columnB and store it to arraylist.
I have try something like this
If myTableData.Rows.Count > 0 Then
For i As Integer = 0 To myTableData.Rows.Count - 1
Dim value() As String = myTableData.Rows(i)(1)
Next
End If
but when I compile that code, I got error message like this :
Unable to cast object of type 'System.String' to type 'System.String[]'
please help me.....
You could do that with LINQ:
Dim colBValues = (From row In myTableData Select colB = row(1).ToString).ToList
Or if you prefer the "old-school" way:
Dim colBValues = New List(Of String)
For Each row As DataRow In myTableData.Rows
colBValues.Add(row(1).ToString)
Next
I've used a List(Of String) because it's type-safe, therefore you don't need to cast the values everytime. That makes code more readable, more failsafe and faster.
If you need it as String-Array, you could simply use ToArray:
Dim colBValues = (From row In myTableData Select colB = row(1).ToString).ToArray
List(T)
LINQ
Dim a() As String
Dim total As Integer
'Count the number of rows
total = myTableData.Rows.Count - 1
ReDim a(0 To total)
For i = 0 To total
a(i) = myTableData.Rows(i)(1)
Next
This is really old question, but I'll provide one more variant of answer :
Dim value = myTableData.Rows.OfType(Of DataRow).Select(Function(x) x(1).ToString()).ToArray
So, if You have more than one column in Your DataTable You can use x(columnIndex) instead 1.