Question

我有一个哈希表，我想从第二个哈希表更新。对于任何匹配的键，我想复制该值。我遇到的问题是当我枚举哈希表键并尝试将每个键转换为字符串时，我收到一个关于将Guid转换为字符串的异常。嗯，这是我想要的字符串。当您使用hashtable [“FirstName”]之类的索引运算符时，我希望FirstName成为键。它可能会使用下面的Guids但我需要输出密钥的字符串，即键值。

private void UpdateSharePointFromInfoPath(Hashtable infopathFields)
{
    // Go through all the fields on the infopath form
    // Invalid Cast Exception Here
    foreach (String fieldName in infopathFields.Keys)
    {
        // If the same field is on sharepoint    
        if (workflowProperties.Item.Fields.ContainsField(fieldName))
        {
            // Update the sharepoint field with the new value from infopath
            workflowProperties.Item[fieldName] = infopathFields[fieldName];
        }
    }
    // Commit the changes
    workflowProperties.Item.Update();
}

修改我不创建这些哈希表中的任何一个。键在某处有字符串，因为我可以像下面这样输入字段名称并获取字段的值。我正在尝试为每个领域做一个简写的方法：

workflowProperties.Item["FirstName"] = infopathFields["FirstName"];
workflowProperties.Item["LastName"] = infopathFields["LastName"];
workflowProperties.Item["Address"] = infopathFields["Address"];
workflowProperties.Item["DOB"] = infopathFields["DOB"];
ect...

修改有人说哈希表使用Guids，但它显然还有一个字符串，否则我就无法做infopathFields [“FirstName”]。这是我在那里传递的字符串的值。

Answer 1

每个项目都是格式为DictionaryEntry的键/值对

foreach (DictionaryEntry de in infopathFields)
        {        
            string fieldName = de.Key as string;         
                if (workflowProperties.Item.Fields.ContainsField(fieldName))        
                {           
                    workflowProperties.Item[fieldName] = infopathFields[fieldName];        
                }    
        }    

        workflowProperties.Item.Update();

Answer 2

Hashtable的标准版本可以有不同的类型键，因此您的大多数键可能是字符串，但您的某些键可能是GUID。我愿意打赌是这种情况，并导致你的问题。以下小控制台应用程序演示了此问题。

    static void Main(string[] args)
    {
        System.Collections.Hashtable htable = new System.Collections.Hashtable();
        htable.Add("MyName", "WindyCityEagle");
        htable.Add("MyAddress", "Here");
        htable.Add(new Guid(), "That Was My Guid");

        int loopCount = 0;
        foreach (string s in htable.Keys)
        {
            Console.WriteLine(loopCount++.ToString());
            Console.WriteLine(htable[s]);
        }
    }

您将获得与此处报告完全相同的异常。

我建议解决问题的方法是使用以下内容

private void UpdateSharePointFromInfoPath(Hashtable infopathFields)
{
    // Go through all the fields on the infopath form
    // Invalid Cast Exception Here
    foreach (object key in infopathFields.Keys)
    {

        string wfpKey = key.ToString();
        // If the same field is on sharepoint    
        if (workflowProperties.Item.Fields.ContainsField(wfpKey))
        {
            // Update the sharepoint field with the new value from infopath
            workflowProperties.Item[wfpKey] = infopathFields[key];
        }
    }
    // Commit the changes
    workflowProperties.Item.Update();
}

Answer 3

创建Hashtable的原因是什么？键实际上是一个对象，所以它听起来像填充它没有隐式强制转换为字符串

Answer 4

如果infopathFields的值类型是Guid，那么workflowProperties的值类型必须是Guids。我无法从代码段中看到workflowProperties定义为什么。

要将Guid转换为字符串，请使用Guid.ToString()

Answer 5

存储在散列表中的对象是Guid对象，因此要获取字符串，您需要在从密钥枚举器获取的对象上调用ToString()。我还建议使用泛型Dictionary<K,V>类而不是Hashtable，因为它会在编译时而不是运行时捕获这样的问题。

Answer 6

从哈希表中获取最大的整数键：

public class Example
{
    public void hashTableMethod()
    {
        Hashtable ht = new Hashtable();
        ht.Add(5002894, "Hemant Kumar");
        ht.Add(5002895, "Himanshee Ratnakar");
        ht.Add(5002896, "Pooja Bhatnagar");
        ht.Add(5002897, "Hina Saxena");
        ht.Add(5002898, "Kanika Aneja");
        ht.Add(5002899, "Hitesh Chaudhary");

        Console.Write("\nNumber of Key-Value pair elements in HashTable are : {0}",ht.Count);
        Console.WriteLine("Elements in HashTable are: ");
        ICollection htkey = ht.Keys;
        foreach (int key in htkey)
        {
            Console.WriteLine("{0}. {1}",key,ht[key]);
        }
        string ch="n";
        do
        {
            Console.Write("\n\nEnter the name to check if it is exist or not, if not then it will add: ");
            string newName=Console.ReadLine();
            if(ht.ContainsValue(newName))
            {
                Console.Write("\nYour Name already Exist in the list!!");
            }
            else
            {
                Console.Write("\nSorry that name doesn't exist but it will be added!!");
                int getKey = 0;

                int[] htk= new int[ht.Count];
                ht.Keys.CopyTo(htk,0);

                string[] val=new string[ht.Count];
                ht.Values.CopyTo(val,0);

                Array.Sort(htk,val);
                foreach (int id in htk)
                {
                    getKey = id;  
                }
                ht.Add(getKey+1,newName);
            }
            Console.Write("\nDo you want to search more??(y/n) :");
            ch=Console.ReadLine();
        }while(ch=="y"||ch=="Y");

        Console.Write("\nNew List Items: \n");
        ICollection htkeys = ht.Keys;
        foreach (int key in htkeys)
        {
            Console.WriteLine("{0}. {1}",key,ht[key]);
        }
    }
}

如何获取Hashtable条目的密钥

6 个答案: