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Render Exceptions in an Entity Framework application

, 8 Feb 2012
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Extension Method for exceptions that give a useful text even on Entity Framework Exceptions

Did you know that exceptions thrown by Entity Framework contain useful information? They are buried in some properties of an inner exception. Here's the code that makes them visible:

public static class Extensions
{
    /// <summary>
    /// Renders an exception with messages and stack traces
    /// </summary>
    /// <param name="ex">The exception to render</param>    
    /// <param name="noTrace">Whether trace information should be omitted</param>
    /// <returns>A string containing messages and stack traces</returns>
    public static string Render(this Exception ex, bool noTrace = false)
    {
        var s = new StringBuilder("\n");
        int i = 0;
        do
        {
            s.AppendFormat("{0:#\\. inner E;;E}xception ({1}):\n   {2}\n", 
                i++, 
                ex.GetType().Name, 
                ex.Message.Replace("\n", "\n   "));
            if (ex is UpdateException)
            {
                foreach (var stateEntry in ((UpdateException)ex).StateEntries)
                {
                    var entity = stateEntry.Entity ?? new object();
                    s.AppendFormat("     {0} {1}: {2}\n", stateEntry.State, entity.GetType().Name, entity);
                    var values =
                        stateEntry.State == EntityState.Deleted
                            ? stateEntry.OriginalValues
                            : stateEntry.CurrentValues;
                    for (int j = 0; j < values.FieldCount; j++)
                    {
                        var currentValue = values[j];
                        var originalValue =
                            stateEntry.State == EntityState.Added
                                ? currentValue
                                : stateEntry.OriginalValues[j];
                        s.AppendFormat(originalValue.Equals(currentValue) ? "      {0}: <{1}>\n" : "      {0}: <{1}>→<{2}\n",
                                       values.GetName(j), originalValue, currentValue);
                    }
                }
            }
            s.AppendFormat(noTrace ? "\n" : "Trace:\n{0}\n", ex.StackTrace);
            ex = ex.InnerException;
        }
        while (ex != null);
        return s.ToString();
    }
}

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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Comments and Discussions

 
GeneralThanks for this snippet. How to properly use them? Please wr... Pinmemberevlntnt16-Feb-12 2:16 
GeneralThe Idea is correct and it is a usefull. But as mentioned by... Pinmemberchrisgl848-Feb-12 9:34 
GeneralI've made a little update that fixed the code for deletes an... PinmemberHarry von Borstel8-Feb-12 3:22 
GeneralReason for my vote of 3 Very nifty tip. nicely done. but is ... PinmemberDean Oliver31-Jan-12 18:30 
GeneralRe: Thanks! Does anyone have an idea how to make it "cleaner"? PinmemberHarry von Borstel31-Jan-12 20:45 
GeneralRe: Thanks! Does anyone have an idea how to make it "cleaner"? PinmemberSandesh Deshmukh10-May-12 9:16 
If its hidden so deep this could easily change in the next version of the entity framework and this could break...
It will happen!

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