/// <summary>
/// 指定された式から値を抽出します。
/// </summary>
/// <param name="expression">対象となる式</param>
/// <returns>値</returns>
/// <remarks>右辺専用</remarks>
private object ExtractValue(Expression expression)
{
//--- 定数
if (expression is ConstantExpression)
{
return(((ConstantExpression)expression).Value);
}
//--- インスタンス生成
if (expression is NewExpression)
{
var expr = (NewExpression)expression;
var parameters = expr.Arguments.Select(this.ExtractValue).ToArray();
return(expr.Constructor.Invoke(parameters));
}
//--- 配列生成
if (expression is NewArrayExpression)
{
var expr = (NewArrayExpression)expression;
return(expr.Expressions.Select(this.ExtractValue).ToArray());
}
//--- メソッド呼び出し
if (expression is MethodCallExpression)
{
var expr = (MethodCallExpression)expression;
var parameters = expr.Arguments.Select(this.ExtractValue).ToArray();
var obj = expr.Object == null
? null //--- static
: this.ExtractValue(expr.Object); //--- instance
return(expr.Method.Invoke(obj, parameters));
}
//--- デリゲート/ラムダ式の呼び出し
if (expression is InvocationExpression)
{
var invocation = (InvocationExpression)expression;
var parameters = invocation.Arguments.Select(x => Expression.Parameter(x.Type)).ToArray();
var arguments = invocation.Arguments.Select(this.ExtractValue).ToArray();
var lambda = Expression.Lambda(invocation, parameters);
var result = lambda.Compile().DynamicInvoke(arguments);
return(result);
}
//--- インデクサ
if (expression is BinaryExpression)
{
if (expression.NodeType == ExpressionType.ArrayIndex)
{
var expr = (BinaryExpression)expression;
var array = (Array)this.ExtractValue(expr.Left);
var index = expr.Right.Type == typeof(int)
? (int)this.ExtractValue(expr.Right)
: (long)this.ExtractValue(expr.Right);
return(array.GetValue(index));
}
}
//--- フィールド / プロパティ
var memberNames = new List <string>();
var temp = expression;
while (!(temp is ConstantExpression))
{
//--- cast
if (temp is UnaryExpression)
{
if (temp.NodeType == ExpressionType.Convert)
{
temp = ((UnaryExpression)temp).Operand;
continue;
}
}
//--- not member
var member = temp as MemberExpression;
if (member == null)
{
return(this.ExtractValue(temp));
}
//--- static
if (member.Expression == null)
{
if (member.Member.MemberType == MemberTypes.Property)
{
var info = (PropertyInfo)member.Member;
return(info.GetValue(null));
}
if (member.Member.MemberType == MemberTypes.Field)
{
var info = (FieldInfo)member.Member;
return(info.GetValue(null));
}
throw new InvalidOperationException("Not field or property.");
}
//--- instance
memberNames.Add(member.Member.Name);
temp = member.Expression;
}
var value = ((ConstantExpression)temp).Value;
for (int i = memberNames.Count - 1; 0 <= i; i--)
{
var getter = AccessorCache.LookupGet(value.GetType(), memberNames[i]);
value = getter(value);
}
return(value);
}
