VB to C# Functions

问题:

Which are the equivalent of the following operators from VB.Net to C#?

• UBound()
• LBound()
• IsNothing()
• Chr()
• Len()
• UCase()
• LCase()
• Left()
• Right()
• RTrim()
• LTrim()
• Trim()
• Mid()
• Replace()
• Split()
• Join()
• MsgBox()
• IIF()

回答1:

VB             C#

UBound()     = yourArray.GetUpperBound(0) or yourArray.Length for one-dimesional arrays
LBound()     = yourArray.GetLowerBound(0)
IsNothing()  = Object.ReferenceEquals(obj,null)
Chr()        = Convert.ToChar()
Len()        = "string".Length
UCase()      = "string".ToUpper()
LCase()      = "string".ToLower()
Left()       = "string".Substring(0, length)
Right()      = "string".Substring("string".Length - desiredLength)
RTrim()      = "string".TrimEnd()
LTrim()      = "string".TrimStart()
Trim()       = "string".Trim()
Mid()        = "string".Substring(start, length)
Replace()    = "string".Replace()
Split()      = "string".Split()
Join()       = String.Join()
MsgBox()     = MessageBox.Show()
IIF()        = (boolean_condition ? "true" : "false")

Notes

• yourArray.GetUpperBound(0) vs yourArray.Length: if the array is zero-length, GetUpperBound will return -1, while Length will return 0. UBound() in VB.NET will return -1 for zero-length arrays.
• The VB string functions uses a one based index, while the .NET method uses a zero based index. I.e. Mid("asdf",2,2) corresponds to "asdf".SubString(1,2).
• ? is not the exact equivalent of IIf because IIf always evaluates both arguments, and ? only evaluates the one it needs. This could matter if there are side effects of the evaluation ~ shudder!
• The Many classic VB String functions, including Len(), UCase(), LCase(), Right(), RTrim(), and Trim(), will treat an argument of Nothing (Null in c#) as being equivalent to a zero-length string. Running string methods on Nothing will, of course, throw an exception.
• You can also pass Nothing to the classic VB Mid() and Replace() functions. Instead of throwing an exception, these will return Nothing.

回答2:

UBound()  "array".Length
LBound()
IsNothing(): "object" == null
Chr()     (char)"N"
Len()     "string".Length
UCase()   "string".ToUpper()
LCase()   "string".ToLower()
Left()    "string".Substring(from, to)
Right()   "string".Substring(from, to)
RTrim()   "string".TrimEnd()
LTrim()   "string".TrimStart()
Trim()    "string".Trim()
Mid()     "string".Substring(from, to)
Replace() "string".Replace()
Split()   "string".Split()
Join()    String.Join()
MsgBox()  MessageBox.Show()
IIF()     validate ? iftrue : iffalse;

回答3:

All these functions are member methods of the Microsoft.VisualBasic.Information class, in the Microsoft.VisualBasic assembly, so you can use them directly. However, most of them have C# equivalents, or non language specific equivalents in core .NET framework classes :

• UBound() : Array.GetUpperBound
• LBound() : Array.GetLowerBound
• IsNothing() : == null
• Chr() : (char)intValue (cast)
• Len() : String.Length
• UCase() : String.ToUpper
• LCase() : String.ToLower
• Left(), Right() and Mid() : String.Substring (with different arguments)
• RTrim() : String.TrimEnd
• LTrim() : String.TrimStart
• Trim() : String.Trim
• Replace() : String.Replace
• Split() : String.Split
• Join() : String.Join
• MsgBox() : MessageBox.Show
• IIF() : condition ? valueIfTrue : valueIfFalse (conditional operator)

Links

• Array members
• String members
• MessageBox.Show
• conditional operator

回答4:

Most of these would be instance methods on the string object that return the modified string.

MsgBox vs. MessageBox.Show(..)

IIF vs. (expression?returnValueIfTrue:returnValueElse)

回答5:

IIf(test, trueval, falseval) >> (test ? trueval : falseval);

IsNothing(obj) >> (obj == null);

UCase(str) >> str.ToUpper();

LCase(str) >> str.ToLower();

回答6:

First of all, most of those are NOT operators. They are functions, and the functions are only included in VB.Net for compatibility reasons. That means you shouldn't use them in VB.net either, and instead use the equivalents provided by the new API.

• UBound() — arrayVar.Length
• LBound() — obsolete, lower bound is always 0 in a normal .Net array
• IsNothing() — obsolete. Use Is Nothing in VB.Net and == null in C#
• Chr() — Convert.ToChar() or (char)someVar
• Len() — stringVar.Length use this in VB too
• UCase() — stringVar.ToUpper() use this in VB too
• LCase() — stringVar.ToLower() use this in VB too
• Left() — stringVar.Substring(0, n) use this in VB too
• Right() — stringVar.Substring(stringVar.Length - n) use this in VB too
• RTrim() — stringVar.TrimEnd() use this in VB too
• LTrim() — stringVar.TrimStart() use this in VB too
• Trim() — stringVar.Trim() use this in VB too
• Mid() — stringVar.Substring(n, m) use this in VB too
• Replace() — stringVar.Replace() use this in VB too
• Split() — stringVar.Split() use this in VB too
• Join() — String.Join() use this in VB too
• MsgBox() — MessageBox.Show()
• IIF() — (condition) ? truepart : falsepart - note that there are some differences, because "?" is an operator and not a function

回答7:

You'll find the conversion for many of these functions on this wikipedia page.

回答8:

I believe some of these like Mid() are still available in the .NET Framework in the Microsoft.VisualBasic namespace which you can still reference from C# code.

回答9:

Another one...

VB - IsDBNull(value)

C# - yourdatarow.IsNull("columnName")

回答10:

If you look on MSDN you see that most of the time there are sample code for both languages.

回答11:

• UBound() -> if x is an array of string[] for example: x.GetUpperBound();
• LBound() -> if x is an array of string[] for example: x.GetLowerBound();
• IsNothing() -> if (x == null)
• Chr() -> char x = (char)65;
• Len() -> x.Length();
• UCase() -> assume x is a string: x.ToUpper();
• LCase() -> assume x is a string: x.ToLower();
• Left() -> assume x is a string: x.Substring(0, 10); // first 10 characters
• Right() -> assume x is a string: x.Substring(x.Length - 10); // last 10 characters
• RTrim() -> x.TrimEnd();
• LTrim() -> x.TrimStart();
• Trim() -> x.Trim();
• Mid() -> assume x is a string: x.Substring()
• Replace() -> assume x is a string: x.Replace();
• Split() -> assume x is a string: x.Split();
• Join() -> String.Join();
• MsgBox() -> MessageBox.Show();
• IIF() -> ternary operator (x == true ? true-value : false-value);

回答12:

One more addition to this could be IndexOf() function to Find String within string

An example below...

string MainString = "String Manipulation"; 
string SearchString = "pul"; 
int FirstChr = MainString.IndexOf(SearchString); 
//SHOWS START POSITION OF STRING 
MessageBox.Show("Found at : " + FirstChr );

回答13:

In addition to the answers above. Be carefull with replacing Len() -> x.Length. VB Len() allows you to pass null, but in c# you will get an exception. Sometimes it would be better to use String.IsNullrEmpty() (If the situation allows)

回答14:

The space function is missing from everyone else's list:

Space(16) -> new String(" ", 16)