Member Avatar for ayagi

Unable to cast object of type 'System.String' to type 'System.Windows.Forms.TextBox'.

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Quick recap tied to earlier replies: and correctly identified two separate issues — assigning a String to a TextBox variable, and an array index going out of range. The IndexOutOfRange in the posted loop comes from forcing i from 0 to 3 even when skillset may have fewer items. A more robust approach is to limit the loop to the smaller of the number of skills and the number of textboxes, and to guard against Nothing/empty elements instead of relying on an empty Catch block.

A safe pattern (map values only while both arrays have entries):

Dim boxes = New TextBox() {txtSkills1, txtSkills2, txtSkills3, txtSkills4}

If skillset IsNot Nothing Then
    Dim count = Math.Min(skillset.Length, boxes.Length)
    For i = 0 To count - 1
        If Not String.IsNullOrEmpty(skillset(i)) Then
            boxes(i).Text = skillset(i)
        Else
            boxes(i).Clear()
        End If
    Next
End If

Notes, cautions and best practices:

  • Avoid calling .ToString without checking for Nothing first; use String.IsNullOrEmpty (or IsNullOrWhiteSpace) to test content. This prevents NullReferenceExceptions.
  • Prefer pre-checks (like the example above) to swallowing exceptions. Empty Catch blocks hide bugs and make debugging harder — during development at least log the exception (Debug.WriteLine or a logger).
  • Turn on Option Strict On and Option Explicit On in project settings; they catch type-assignment mistakes at compile time (the string-to-textbox problem).
  • Use the debugger/watch window to inspect skillset.Length and individual elements when tracing an IndexOutOfRangeException.

These changes keep the UI code predictable and avoid the two errors discussed by and .

Recommended Answers

All 12 Replies

Member Avatar for bLuEmEzzy

you can not convert string to textbox.

Member Avatar for codeorder 
TextBox1 = ""

The above line will cause this error: Value of type 'String' cannot be converted to 'System.Windows.Forms.TextBox'. Can easily be fixed by setting the .Text of the TextBox as the String, and not the TextBox it's self.

TextBox1.Text = ""

Without your code that generates the error, it is difficult for someone to exactly recreate it.

Member Avatar for ayagi

thanks.
i already solve it.

i have a problem in my array.. it says "Index was outside the bounds of the arrays"

what is the error handled in that problem?
here is my code

For i As Integer = 0 To 3
                        If i = 0 And skillset(i).ToString <> vbNullString Then
                            txtSkills1.Text = skillset(i).ToString
                        End If
                        If i = 1 And skillset(i).ToString <> vbNullString Then
                            txtSkills2.Text = skillset(i).ToString
                        End If
                        If i = 2 And skillset(i).ToString <> vbNullString Then
                            txtSkills3.Text = skillset(i).ToString
                        End If
                        If i = 3 And skillset(i).ToString <> vbNullString Then
                            txtSkills4.Text = skillset(i).ToString
                        End If
Member Avatar for codeorder

>>it says "Index was outside the bounds of the arrays"

This usually occurs when your (i) goes over the Array length/count.
.Here's an example.

Try
            Dim arTemp() As String = {"one", "two", "three"}
            MsgBox(arTemp(3))
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try

Since Arrays start at 0 not 1, the arTemp(3) is actually Array 4, which is not included in my declared Array. Therefore you will get the error message.

Edited by codeorder because: n/a
Member Avatar for ayagi

i dont get it :(

Member Avatar for codeorder

Ok. With the above posted code, using MsgBox(arTemp(0)) , you will get "one", MsgBox(arTemp(1)) will get you "two", and MsgBox(arTemp(2)) will get you "three" from the arTemp String Array.
.Since in my code I had MsgBox(arTemp(3)) , that Array does not exist in arTemp, which should return a "four", therefore you get the error of "Index was outside the bounds of the Array".

Basically saying, that error will let you know when you are trying to locate something that is not there, it is "outside the bounds", bounds meaning Array length/count.

Edited by codeorder because: added content
Member Avatar for ayagi

how can i trap that error?
if i don't have the value for that array, i will display nothing in my textbox..

Member Avatar for codeorder

Change MsgBox(ex.Message) to TextBox1.Clear in the Try/Catch of my previously posted code.

Try
            '// run all code here that can/might cause an error.
        Catch ex As Exception
            '// add code here to correct the error if it does occur.
        End Try
Edited by codeorder because: title added
Member Avatar for ayagi

ok i get it.. :) thanks

Member Avatar for ayagi

if i don't write any code in catch ex as exception.
the error will not display ..

Member Avatar for codeorder

Correct.

Member Avatar for ayagi

thanks its really help.
i feel so upset not solving that error.
i just new in .net programming.
:) thank you so much :)

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