Question

I want to write an user defined error collection class which should collect all the Error’s. When we validate an entity object if there is no error it should go and save to the Database. if Error there it should display it.
now i have wrote the class it collects the error and displays it successfully but when there is two identical error the class throws an exception.
(i use error-code for the error. the value for the error-code is in resx file from where the display method will take the value and display it. Display works perfectly)

//The code where it collects Error 
if (objdepartment.Departmentname == null)
{
    ErrorCollection.AddErrors("A1001","Department Name");
}
if (objdepartment.Departmentcode == null)
{
    ErrorCollection.AddErrors("A1001","Department code");
}

//In the Errorcollection  

public class ErrorCollection
{
    static Dictionary<string,List<string>> ErrorCodes;
    private ErrorCollection() { }

    public static void AddErrors(string eCode,params string[] dataItem)
    {
        if (ErrorCodes == null)
        {
            ErrorCodes = new Dictionary<string, List<string>>();
        }
        List<String> lsDataItem = new List<String>();
        foreach (string strD in dataItem)            
            lsDataItem.Add(strD);
        ErrorCodes.Add(eCode, lsDataItem);
    }

    public static string DisplayErrors()
    {
        string ErrorMessage;
        //string Key;
        ErrorMessage = String.Empty;
        if (ErrorCodes != null)
        {
            string Filepath= "D:\\Services\\ErrorCollection\\";
            //Read Errors- Language Specsific message from resx file.
            ResourceManager rm = ResourceManager.CreateFileBasedResourceManager("ErrorMessages", Filepath, null);
            StringBuilder sb = new StringBuilder();
            foreach (string error in ErrorCodes.Keys)
            {                
                List<string> list = ErrorCodes[error];
                if (error == "A0000")
                {
                    sb.Append("System Exception : " + list[0]);
                }
                else
                {
                    sb.Append(rm.GetString(error) + "\nBreak\n");
                }

                for (int counter = 0; counter < list.Count; counter++)
                {
                    sb.Replace("{A}", list[counter]);
                }
            }
            ErrorMessage = sb.ToString();
        }
        return ErrorMessage;
    }
}    

now when there is two common error. then the code shows an exception like “datakey already exist” in the line ” ErrorCodes.Add(eCode, lsDataItem);” (the italic part where the exception throwed)

Answer 1

You are adding “A1001” twice as a key in a dictionary. That simply isn’t allowed. However, more urgently – why is that dictionary static? That means that everything, anywhere, shares that error collection.

Suggestions:

• make that not static (that is a bad idea – also, it isn’t synchronized)

• check for existence of the key, and react accordingly:

  if(ErrorCodes.ContainsKey(eCode)) ErrorCodes[eCode].AddRange(lsDataItem);
  else ErrorCodes.Add(eCode, lsDataItem);
  

As an aside, you might also consider implementing IDataErrorInfo, which is a built-in standard wrapper for this type of functionality, and will provide support for your error collection to work with a few standard APIs. But don’t rush into this until you need it ;p