// Associates the action method argument to the corresponding resource property
// used to populate the argument. This is used when sending the route-info to
// ASP.NET Core to resolve the corresponding URL.
private void SetRouteValues(LambdaExpression expression)
{
// The specified controller action declared method parameters:
var controllerAction = (MethodCallExpression)expression.Body;
var actionParams = controllerAction.Method.GetParameters()
.OrderBy(p => p.Position)
.ToArray();
for (int i = 0; i < controllerAction.Arguments.Count; i++)
{
// The input argument to the action method parameter:
var passedArg = controllerAction.Arguments[i];
if (passedArg is MemberExpression propExpArg)
{
var propInfo = (PropertyInfo)propExpArg.Member;
var actionParam = actionParams[i];
var routeValue = new RouteParameter(actionParam.Name, propInfo);
_resourceLink.AddRouteValue(routeValue);
continue;
}
// This is the case when the action parameter specifies a default value.
if (passedArg is UnaryExpression unaryExpArg)
{
var operand = (MemberExpression)unaryExpArg.Operand;
var propInfo = (PropertyInfo)operand.Member;
var actionParam = actionParams[i];
var routeValue = new RouteParameter(actionParam.Name, propInfo);
_resourceLink.AddRouteValue(routeValue);
}
}
}
/// <summary>
/// Adds a mapping indicating the resource property corresponding to an action parameter.
/// </summary>
/// <param name="routeParam">Mapping between action parameter and corresponding resource property.</param>
public void AddRouteValue(RouteParameter routeParam)
{
if (routeParam == null)
{
throw new ArgumentNullException(nameof(routeParam),
"Route parameter cannot be null.");
}
if (_routeValues.Any(rv => rv.ActionParamName == routeParam.ActionParamName))
{
throw new ArgumentException($"The action parameter named: {routeParam.ActionParamName} has already been added.");
}
_routeValues.Add(routeParam);
}
