"Conversion from string to type Double is not valid" error VB.NET

Question

I'm trying to display a logged in users balance from a database in VB. However once I click the Check Balance button it produces the error `Conversion from string "Your balance is " to type 'Double' is not valid`. I've tried different ways a converting it from a string to a double, I thought maybe it was because I had m_decBalance declared as a decimal, but that didn't change anything. Can anyone help me? Here's my code: ``` Imports MySql.Data Imports MySql.Data.MySqlClient Public Class Form1 Dim dbCon As MySqlConnection Dim strQuery As String = "" Dim SQLcmd As MySqlCommand Dim DataReader As MySqlDataReader Private m_strPass As String Private m_decBalance As Decimal Private m_strName As String Private m_strUserPass As String Private m_strCardNumber As String Private Sub Button2_Click(sender As Object, e As EventArgs) Handles btnLogin.Click 'Assign users guessed password to variable m_strUserPass = txtPass.Text 'Invoke RetrieveAccountInformation() ' determine if Password is correct or…

Accepted Answer

The problem is that you are joining a string with a `+`. You need to replace the `+` with `&`. I also recommend adding `.ToString` to your `m_decBalance`, as this will tell the compiler to treat `m_decBalance` as a `string`, like so:

```
MsgBox("You balance is " & " " & m_decBalance.ToString)
```

The reason you are getting the error is that the compiler tries to convert the string to a numeric value when `+` is used with a number. For example, the following will display a messagebox with the value of `10`:

```
MsgBox("5 " + " " + 5)
```

and

```
Dim Val As Integer = "20 " + 15
```

will result in `Val` being `35`

When you want to join strings, I recommend using the `&`, as this tells the compiler that you don't wish to convert the string to a number, and instead you wish to join them as strings.

I would also like to suggest using `Option Strict On`, as this will help prevent errors like this from happening, as it prevent you from recompiling if you have any `implicit conversions` (where the compiler has to guess which type you want to convert to)

"Conversion from string to type Double is not valid" error VB.NET

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