for loop for a string variable

Question

this is my code -

for i as integer = 0 to rows.count - 1
   output &= "Name =" & row(i)("Name")
   output &= "lastName =" & row(i)("lastName")
... 50 more fields
next

i need the output to be like this

Applicant1Name = MikeApplicant1lastName = ditkaApplicant2Name = TomApplicant2lastName = Brady ...

how do i do this without putting the following code 50 times - output &= "Applicant" & i.tostring() + 1 &"Name =" & row(i)("Name") ... and so on. is there a way to make a for loop and run applicant 1,2,3,4.... in one shot? thanks

Joel Etherton · Accepted Answer · 2010-02-23 18:32:29Z

6

Try:

Dim output as New StringBuilder("")

For i as Integer = 0 To rows.Count - 1
    output.append("Applicant" + i.ToString())
    Foreach(col as DataColumn in dt.Columns)  ' The datatable where your rows are
        Dim colName as string = col.ColumnName
        output.append(colName & "=" & rows(i)(colName).ToString())
    Next
    If i < rows.Count - 1 Then output.Append("|")
Next

StringBuilder is faster for string concatenations, and if you keep your rows in a datatable (which I assume is happening because that's how it looks like you're accessing them), then you can just iterate through the columnnames at the top level.

answered Feb 23, 2010 at 18:32

Joel Etherton

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5 Comments

Teekin Over a year ago

+1 for the correct answer, and I'd give you +2 if I could for mentioning using StringBuilder. It is hard to exaggerate the performance impact of concatenating lots of text with the use of strings only.

iregy Over a year ago

the line - Foreach(col as DataColumn in dt.Columns), where do i declare col?

Joel Etherton Over a year ago

@iregy - col is declared in that line as a DataColumn. By doing it inside the () there, you keep its scope to the immediate block.

iregy Over a year ago

it gives me an error saying "Name 'col' is not declared" this is the code i made - With ds.Tables(2) For i As Integer = 0 To .Rows.Count - 1 output.Append("Applicant") For Each (col As DataColumn In ds.Tables(2)) output.Append("GivenName||" & .Rows(i)("firstname") & vbCrLf) output.Append("LastName||" & .Rows(i)("lastname") & vbCrLf) Next If i < .Rows.Count - 1 Then output.Append("||") Next End With

Joel Etherton Over a year ago

@iregy: Given that you've used the "With" keyword, you'll need to declare col in the for each this way --> For Each (col as DataColumn In .Columns)

JonH · Accepted Answer · 2010-02-23 18:25:59Z

0

You really cant as you are trying to append 50 different fields. The only thing you can shorten is the variable name:

Dim strLN as String = row(i)("lastName")
Dim strFirstName as String = row(i)("firstName")

Then you simply put it all together

output &= strLN & strFirstName...etc

answered Feb 23, 2010 at 18:25

JonH

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1 Comment

iregy Over a year ago

where is the "Applicant" part? i need Applicant1Name,Applicant2Name and so on for like 50 more fields

NerdFury · Accepted Answer · 2010-02-23 18:32:24Z

0

looks like you want to create an array of all the fields you have and then include a nested loop.

    Dim fields As String() = {"Name", "LastName", "SSN", "Birthdate"}
    Dim output As String = ""

    For i As Integer = 1 To rows.count
        For Each field As String In fields
            output = String.Concat(output, "Applicant ", i, field, "=", row(i)(field), " ")
        Next
    Next

answered Feb 23, 2010 at 18:32

NerdFury

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2 Comments

Teekin Over a year ago

That is unnecessary. He can loop through the already existing columns. Still better in my opinion than having to list all the fields individually.

NerdFury Over a year ago

True, didn't think about that. The part of my brain that stores information about DataSets and DataTables has atrophied from excessive ORM use.

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