如何清理web api過濾器中字符串參數的值？

Question

我有web api應用程序，我想使用web api過濾器清理來自前端應用程序的數據。

我創建了以下過濾器：

public class StringFilter : ActionFilterAttribute 
{ 
    public override void OnActionExecuting(HttpActionContext actionContext) 
    { 
     foreach (var actionArgument in actionContext.ActionArguments) 
     { 
      if (actionArgument.Value.GetType() == typeof(string)) 
      { 
       var sanitizedString = actionArgument.Value.ToString().Trim(); 
       sanitizedString = Regex.Replace(sanitizedString, @"\s+", " "); 
       actionContext.ActionArguments[actionArgument.Key] = sanitizedString; 
      } 
      else 
      { 
       var properties = actionArgument.Value.GetType().GetProperties(BindingFlags.Instance | BindingFlags.Public) 
        .Where(x => x.CanRead && x.PropertyType == typeof(string) && x.GetGetMethod(true).IsPublic && x.GetSetMethod(true).IsPublic); 
       foreach (var propertyInfo in properties) 
       { 
        var sanitizedString = propertyInfo.GetValue(actionArgument.Value).ToString().Trim(); 
        sanitizedString = Regex.Replace(sanitizedString, @"\s+", " "); 
        propertyInfo.SetValue(actionArgument.Value, sanitizedString); 
       } 
      } 
     } 

    } 
} 

這段代碼的問題是裏面的代碼if語句，我想消毒作爲單個字符串傳遞的參數，我得到這個錯誤：

"ClassName": "System.InvalidOperationException", "Message": "Collection was modified; enumeration operation may not execute.

但是，如果我的web api動作將一個參數作爲具有字符串屬性的dto對象，則代碼（它位於else語句中）完美工作，字符串在開始執行動作之前已經過清理。

所以我的問題如何清理傳遞的參數，以防萬一它是字符串參數？

Answer 1

您正在嘗試在枚舉它的同時修改相同的集合，這是不允許的。請致電.ToList()，以便在修改原稿時枚舉單獨的集合。即foreach (var actionArgument in actionContext.ActionArguments.ToList()) {...

public override void OnActionExecuting(HttpActionContext actionContext) { 
    foreach (var actionArgument in actionContext.ActionArguments.ToList()) { 
     if (actionArgument.Value != null && actionArgument.Value is string) { 
      var sanitizedString = actionArgument.Value.ToString().Trim(); 
      sanitizedString = Regex.Replace(sanitizedString, @"\s+", " "); 
      actionContext.ActionArguments[actionArgument.Key] = sanitizedString; 
     } else { 
      var properties = actionArgument.Value.GetType().GetProperties(BindingFlags.Instance | BindingFlags.Public) 
       .Where(x => x.CanRead && x.PropertyType == typeof(string) && x.GetGetMethod(true).IsPublic && x.GetSetMethod(true).IsPublic); 
      foreach (var propertyInfo in properties) { 
       var sanitizedString = propertyInfo.GetValue(actionArgument.Value).ToString().Trim(); 
       sanitizedString = Regex.Replace(sanitizedString, @"\s+", " "); 
       propertyInfo.SetValue(actionArgument.Value, sanitizedString); 
      } 
     } 
    } 
}