Expression to pretty string template

ExpressionToPrettyString.cs

public static class ToStringExpressionVisitorExtensions
{
   public static string ToPrettyString(this IQueryable @this)
   {
       var v = new ToStringExpressionVisitor();
       v.Visit(@this.Expression);
       return v.sb.ToString();
   }
}

class ToStringExpressionVisitor : ExpressionVisitor
{
   public StringBuilder sb = new StringBuilder();
   

   protected override Expression VisitBinary(BinaryExpression node)
   {
       Visit(node.Left);
       sb.Append(" ").Append(node.NodeType).Append(" "); // switch here to have prettier results
       Visit(node.Right);
       return node;
   }

   protected override Expression VisitMethodCall(MethodCallExpression node)
   {
       if(node.Method.DeclaringType == typeof(Queryable)){
           // special case for .Where, .Select, etc ? 
       }
       if (node.Object != null)
           Visit(node.Object);
       sb.Append(node.Method.Name).Append("(");
       int x = 0;
       foreach (var a in node.Arguments)
       {
           if (x++ > 0)
               sb.Append(", ");
           Visit(a);
       }
       sb.Append(")");
       return node;
   }

   protected override Expression VisitLambda<T>(Expression<T> node)
   {
       if (node.Parameters.Count == 1)
           sb.Append(Visit(node.Parameters[0]));
       else
           sb.Append("(").Append(string.Join(",", node.Parameters.Select(x => x.Name))).Append(")");

       sb.Append(" => ");
       Visit(node.Body);
       return node;
   }

   protected override Expression VisitParameter(ParameterExpression node)
   {
       sb.Append(node.Name);
       return node;
   }

   protected override Expression VisitMember(MemberExpression node)
   {
       Visit(node.Expression);
       sb.Append(".").Append(node.Member.Name);
       return node;
   }

   protected override Expression VisitConstant(ConstantExpression node)
   {
       var constant = node.Value;
       if(constant is IEnumerable) // special case depending on constant type ?
       {
       }
       if(constant is string)
       {
           sb.Append('"').Append(constant).Append('"');
       }
       sb.Append(constant == null ? "null" : constant.ToString());
       return node;
   }

   protected override MemberBinding VisitMemberBinding(MemberBinding node)
   {
       // todo
       return base.VisitMemberBinding(node);
   }

   protected override Expression VisitMemberInit(MemberInitExpression node)
   {
       // todo
       return base.VisitMemberInit(node);
   }

   protected override Expression VisitNew(NewExpression node)
   {
       // todo
       return base.VisitNew(node);
   }


   protected override Expression VisitNewArray(NewArrayExpression node)
   {
       // todo

       return base.VisitNewArray(node);
   }

   protected override Expression VisitUnary(UnaryExpression node)
   {
       return base.VisitUnary(node);
   }
}