public static bool TryCreate(
SyntaxNode node,
SemanticModel semanticModel,
out NullCheckExpression result,
CancellationToken cancellationToken = default(CancellationToken))
{
if (node != null)
{
var expression = node as ExpressionSyntax;
if (expression != null)
{
expression = expression.WalkDownParentheses();
SyntaxKind kind = expression.Kind();
switch (kind)
{
case SyntaxKind.EqualsExpression:
case SyntaxKind.NotEqualsExpression:
{
var binaryExpression = (BinaryExpressionSyntax)expression;
ExpressionSyntax left = binaryExpression.Left?.WalkDownParentheses();
ExpressionSyntax right = binaryExpression.Right?.WalkDownParentheses();
return(TryCreate(binaryExpression, kind, left, right, semanticModel, cancellationToken, out result) ||
TryCreate(binaryExpression, kind, right, left, semanticModel, cancellationToken, out result));
}
case SyntaxKind.SimpleMemberAccessExpression:
{
if (SemanticUtilities.IsPropertyOfNullableOfT(expression, "HasValue", semanticModel, cancellationToken))
{
var memberAccessExpression = (MemberAccessExpressionSyntax)expression;
result = new NullCheckExpression(expression, memberAccessExpression.Expression, NullCheckKind.HasValue);
return(true);
}
break;
}
case SyntaxKind.LogicalNotExpression:
{
var logicalNotExpression = (PrefixUnaryExpressionSyntax)expression;
ExpressionSyntax operand = logicalNotExpression.Operand?.WalkDownParentheses();
if (operand?.IsKind(SyntaxKind.SimpleMemberAccessExpression) == true &&
SemanticUtilities.IsPropertyOfNullableOfT(operand, "HasValue", semanticModel, cancellationToken))
{
var memberAccessExpression = (MemberAccessExpressionSyntax)operand;
result = new NullCheckExpression(expression, memberAccessExpression.Expression, NullCheckKind.NotHasValue);
return(true);
}
break;
}
}
}
}
result = default(NullCheckExpression);
return(false);
}
/// <summary>
/// Returns the string representation of the underlying syntax, not including its leading and trailing trivia.
/// </summary>
/// <returns></returns>
public override string ToString()
{
return(NullCheckExpression?.ToString() ?? "");
}
private static bool TryCreate(
BinaryExpressionSyntax binaryExpression,
SyntaxKind kind,
ExpressionSyntax expression1,
ExpressionSyntax expression2,
SemanticModel semanticModel,
CancellationToken cancellationToken,
out NullCheckExpression result)
{
if (expression1 != null &&
expression2 != null)
{
switch (expression1.Kind())
{
case SyntaxKind.NullLiteralExpression:
{
result = new NullCheckExpression(
binaryExpression,
expression2,
(kind == SyntaxKind.EqualsExpression) ? NullCheckKind.EqualsToNull : NullCheckKind.NotEqualsToNull);
return(true);
}
case SyntaxKind.TrueLiteralExpression:
{
if (expression2?.IsKind(SyntaxKind.SimpleMemberAccessExpression) == true &&
SemanticUtilities.IsPropertyOfNullableOfT(expression2, "HasValue", semanticModel, cancellationToken))
{
result = new NullCheckExpression(
binaryExpression,
((MemberAccessExpressionSyntax)expression2).Expression,
(kind == SyntaxKind.EqualsExpression) ? NullCheckKind.HasValue : NullCheckKind.NotHasValue);
return(true);
}
break;
}
case SyntaxKind.FalseLiteralExpression:
{
if (expression2?.IsKind(SyntaxKind.SimpleMemberAccessExpression) == true &&
SemanticUtilities.IsPropertyOfNullableOfT(expression2, "HasValue", semanticModel, cancellationToken))
{
result = new NullCheckExpression(
binaryExpression,
((MemberAccessExpressionSyntax)expression2).Expression,
(kind == SyntaxKind.EqualsExpression) ? NullCheckKind.NotHasValue : NullCheckKind.HasValue);
return(true);
}
break;
}
}
}
result = default(NullCheckExpression);
return(false);
}