.NET: How to convert Exception to string?

ErrorCode is specific to ExternalException, not Exception and LineNumber and Number are specific to SqlException, not Exception. Therefore, the only way to get these properties from a general extension method on Exception is to use reflection to iterate over all of the public properties.

So you’ll have to say something like:

public static string GetExceptionDetails(this Exception exception) {
    var properties = exception.GetType()
                            .GetProperties();
    var fields = properties
                     .Select(property => new { 
                         Name = property.Name,
                         Value = property.GetValue(exception, null)
                     })
                     .Select(x => String.Format(
                         "{0} = {1}",
                         x.Name,
                         x.Value != null ? x.Value.ToString() : String.Empty
                     ));
    return String.Join("\n", fields);
}

(Not tested for compliation issues.)

.NET 2.0 compatible answer:

public static string GetExceptionDetails(this Exception exception) 
{
    PropertyInfo[] properties = exception.GetType()
                            .GetProperties();
    List<string> fields = new List<string>();
    foreach(PropertyInfo property in properties) {
        object value = property.GetValue(exception, null);
        fields.Add(String.Format(
                         "{0} = {1}",
                         property.Name,
                         value != null ? value.ToString() : String.Empty
        ));    
    }         
    return String.Join("\n", fields.ToArray());
}