csharp-coding-style.md

C# Coding Style

We use the same coding style and EditorConfig file (.editorconfig) used by dotnet/runtime with the following differences:

• var must be used when new, as, or cast operator is used (and it can be used only with these operators).

  var foo = new Foo(); // OK
  Foo foo = new Foo(); // NOT OK
  
  var bar = foo as Bar; // OK
  Bar bar = foo as Bar; // NOT OK
  
  var bar = (Bar)foo; // OK
  Bar bar = (Bar)foo; // NOT OK
  
  string str = "hello"; // OK
  var str = "hello"; // NOT OK
  int i = 0; // OK
  var i = 0; // NOT OK
  
  var arr = new string[] { "abc", "def" }; // OK
  string[] arr = new[] { "abc", "def" }; // NOT OK
  var arr = new[] { "abc", "def" }; // NOT OK
  
  string str = foo.GetString(); // Function name shouldn't matter.
  var str = foo.GetString(); // NOT OK

• A single line statement block must go with braces.

  // OK
  if (foo)
  {
      return false;
  }
  
  // NOT OK
  if (foo) return false;
  if (foo) { return false };

• Use prefix increment/decrement operator.

  Unless post increment/decrement operator usage is intended, use prefix increment/decrement operator.

  // OK
  for (int i = 0; i < arr.Length; ++i)
  
  // NOT OK
  for (int i = 0; i < arr.Length; i++)
  
  // OK
  arr[i++]; // Post increment operator usage is intended.

• The max number of characters in a line is 110.

  This can be easily done using the following line-break rules:

  (If you cannot find a rule for your scenario, please look through the existing code to find a match and create an issue to update this list.)

  • Line-break for the assignment

  // Try the following first to fit within the limit.
  SomeType someVariable =
      SomeMethod(arg1, arg2, arg3, arg4, arg5);
     
  // Then fall back to this.
  SomeType someVariable = SomeMethod(
      arg1,
      arg2,
      arg3,
      arg4,
      arg5);

  • Line-break for each method parameters:

  return UserDefinedFunction.Create(
      name,
      CommandSerDe.Serialize(
          execute,
          CommandSerDe.SerializedMode.Row,
          CommandSerDe.SerializedMode.Row),
      UdfUtils.GetPythonEvalType(),
      UdfUtils.GetReturnType(typeof(RT)));

  • Line-break for each method call:

  // If you have chained method calls, line-break each method call
  Enumerable.Range(0, numRows)
      .Select(i => i.ToString())
      .ToArray();

  There are few exceptions to this rule:

  • Log message with string interpolation:

  Logger.LogInfo($"This message {someVariable} is too long but try your best to fit in 100 character limit.");

  • The method signature without method parameters is long due to type paramters:

  public static Func<Column, Column, Column, Column, Column, Column, Column, Column, Column, Column, Column> Udf<A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, RT>(
      Func<A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, RT> udf)