C# to VB: Converting to Boolean

Question

User-567435310 posted

I am converting some C# code to VB, the following code is part of a function

if (bool.Parse(v["Parent"].ToString()))
{
e.Row.CssClass = "Parent";
}

V is System.Data.DataRowView When I convert this to…

If Boolean.Parse(v("Parent").ToString()) Then
	e.Row.CssClass = "Parent"
End If

The code throws an error “String was not recognized as a valid Boolean” But if I use this code

If CBool(v("Parent").ToString) = True Then
e.Row.CssClass = "Parent"
End If

It works fine, which is great, I am just curious why?

Answer 1

User1224194097 posted

Convert.ToBoolean and Boolean.Parse fails to convert the value to boolean either true or false when the argument is null

So I suggest using Boolean.TryParse which checks if the argument is a valid boolean argument or not.

That way you can ensure that your code does not fail

check this link

http://msdn.microsoft.com/en-us/library/system.boolean.tryparse.aspx

Both are same but Tryparse does not throw an exception when conversion fails whereas Parse throws an error

Answer 2

User1080785583 posted

Boolean.parse parses a string value.

CBool converts an EXPRESSION to boolean. 

If Boolean.Parse(1 > 0) Then

' we are ok

'if you use OPTION SCRIPT ON and OPTION EXPLICIT ON you will get conversion error, otherwise you are ok

End If

 

If Boolean.Parse("string") Then

'compiler does not catch this error but will result in an error once executed

 End If

 

Answer 3

User-567435310 posted

I know that the value being passed through is not null, having debugged and stepped through the code.

If Boolean.Parse parses a string value, I am confused why this will not work. The value being passed to the function is a bit value from a SQL database and it is being passed through as a string.

Any thoughts?

Answer 4

User1080785583 posted

You parse like this.

http://msdn.microsoft.com/en-us/library/system.boolean.parse.aspx

 

Answer 5

User-660870441 posted

Hi,

Bool.Prase() method only accept a specific string (“true”, “false”), if the parameter is null or other strings, it will throws that exception.

For example:

Boolean.Prase(“true”) // return true

Boolean.prase(“1”) // throw exception

Boolean.prase(Nothing) // throw exception

 

CBool() method works just in C language, the parameter is any object.

For example:

CBool(2) // return true

CBool(“2”) // return true

CBool(Nothing) // return true

I recommend you using Boolean.TryParse() method since it won’t throw exception.

 

 

Answer 6

User-567435310 posted

You are correct that Boolean.Parse will only accept a specific string. But CBool also works in vb.net

http://msdn.microsoft.com/en-us/library/2k9sfx3c(VS.85).aspx 

Answer 7

User-660870441 posted

Sorry about my typing. As you said, of course CBool works in VB.NET. I want to said is that CBool works like a bool expression in C language. It treats an integer 1 as true and a not null object as true.

If I misunderstood you, please feel free to let me know.

 

Answer 8

User1048247244 posted

If you get stuck on a part, check out http://converter.telerik.com/. It's not 100%, but it's not bad either.