First, get the VariableDeclaratorSyntax
for your variable, for example:
var variable = tree.GetRoot().DescendantNodes()
.OfType<VariableDeclaratorSyntax>()
.Single(v => v.Identifier.ValueText == "myString");
Next, get the LocalSymbol
for this variable from the SemanticModel
:
var variableSymbol = (LocalSymbol)model.GetDeclaredSymbol(variable);
Then you can get a list of methods you can invoke on this variable based on its type. You can either simply get all members of the type that are instance methods:
var methods =
variableSymbol.Type.GetMembers()
.OfType<MethodSymbol>()
.Where(m => !m.IsStatic && m.MethodKind == MethodKind.Ordinary);
Or, if you wanted to include extension methods, you could use LookupSymbols()
:
var methods = model.LookupSymbols(
variable.GetLocation().SourceSpan.Start, variableSymbol.Type,
options: LookupOptions.IncludeExtensionMethods)
.Where(m => !m.IsStatic);
You can then choose one of the available methods based on your logic and create InvocationExpressionSyntax
(the following code assumes it's a parameterless method):
var invocationExpression =
Syntax.InvocationExpression(
Syntax.MemberAccessExpression(
SyntaxKind.MemberAccessExpression,
Syntax.IdentifierName(variableSymbol.Name),
(SimpleNameSyntax)Syntax.ParseName(selectedMethod.Name)));
You would then need to figure out where in your method to add the expression and what to do with its result (if anything).