Creates SqlException through reflection and sets ErrorMessage and ErrorCode. Be aware this reflects private functionality which is likely to change, do not use this in production code

SqlExceptionCreator

using System;
using System.Collections;
using System.Collections.Generic;
using System.Reflection;
using System.Runtime.Serialization;
using System.Data.SqlClient;

public static class SqlExceptionCreator
{
	public static SqlException Create(string message, int errorCode)
	{
		SqlException exception = Instantiate<SqlException>();
		SetProperty(exception, "_message", message);

		var errors = new ArrayList();

		var errorCollection = Instantiate<SqlErrorCollection>();
		SetProperty(errorCollection, "errors", errors);

		var error = Instantiate<SqlError>();
		SetProperty(error, "number", errorCode);
		errors.Add(error);

		SetProperty(exception, "_errors", errorCollection);

		return exception;
	}

	private static T Instantiate<T>() where T : class
	{
		return FormatterServices.GetUninitializedObject(typeof(T)) as T;
	}

	private static void SetProperty<T>(T targetObject, string fieldName, object value)
	{
		var field = typeof(T).GetField(fieldName, BindingFlags.NonPublic | BindingFlags.Instance);
		if (field != null)
		{
			field.SetValue(targetObject, value);
		}
		else
		{
			throw new InvalidOperationException("No field with name " + fieldName);
		}
	}
}