public static Type Build(TypeMeta meta)
        {//需增加一个判断
            TypeBuilder            builder = moduleBuilder.DefineType(meta.TypeName, TypeAttributes.Public);
            CustomAttributeBuilder tableAttributeBuilder = new CustomAttributeBuilder(typeof(TableAttribute).GetConstructor(new Type[1] {
                typeof(string)
            }), new object[] { "RuntimeModel_" + meta.TypeName });

            builder.SetParent(meta.BaseType);
            builder.SetCustomAttribute(tableAttributeBuilder);

            foreach (var item in meta.PropertyMetas)
            {
                AddProperty(item, builder, meta.BaseType);
            }
            return(builder.CreateTypeInfo().UnderlyingSystemType);
        }
        //这个方法就是把一个RuntimeModelMeta转换成更接近类结构的TypeMeta对象
        private TypeMeta GetTypeMetaFromModelMeta(RuntimeModelMeta meta)
        {
            TypeMeta typeMeta = new TypeMeta();

            //我们让所有的动态类型都继承自DynamicEntity类,这个类主要是为了方便属性数据的读取,具体代码看后面
            typeMeta.BaseType = typeof(DynamicEntity);
            typeMeta.TypeName = meta.ClassName;

            foreach (var item in meta.ModelProperties)
            {
                TypeMeta.TypePropertyMeta pmeta = new TypeMeta.TypePropertyMeta();
                pmeta.PropertyName = item.PropertyName;
                //如果必须输入数据,我们在属性上增加RequireAttribute特性,这样方便我们进行数据验证
                if (item.IsRequired)
                {
                    TypeMeta.AttributeMeta am = new TypeMeta.AttributeMeta();
                    am.AttributeType  = typeof(RequiredAttribute);
                    am.Properties     = new string[] { "ErrorMessage" };
                    am.PropertyValues = new object[] { "请输入" + item.Name };
                    pmeta.AttributeMetas.Add(am);
                }

                if (item.ValueType == "string")
                {
                    pmeta.PropertyType = typeof(string);
                    TypeMeta.AttributeMeta am = new TypeMeta.AttributeMeta();
                    //增加长度验证特性
                    am.AttributeType        = typeof(StringLengthAttribute);
                    am.ConstructorArgTypes  = new Type[] { typeof(int) };
                    am.ConstructorArgValues = new object[] { item.Length };
                    am.Properties           = new string[] { "ErrorMessage" };
                    am.PropertyValues       = new object[] { item.Name + "长度不能超过" + item.Length.ToString() + "个字符" };

                    pmeta.AttributeMetas.Add(am);
                }
                else if (item.ValueType == "int")
                {
                    if (!item.IsRequired)
                    {
                        pmeta.PropertyType = typeof(int?);
                    }
                    else
                    {
                        pmeta.PropertyType = typeof(int);
                    }
                }
                else if (item.ValueType == "datetime")
                {
                    if (!item.IsRequired)
                    {
                        pmeta.PropertyType = typeof(DateTime?);
                    }
                    else
                    {
                        pmeta.PropertyType = typeof(DateTime);
                    }
                }
                else if (item.ValueType == "bool")
                {
                    if (!item.IsRequired)
                    {
                        pmeta.PropertyType = typeof(bool?);
                    }
                    else
                    {
                        pmeta.PropertyType = typeof(bool);
                    }
                }
                typeMeta.PropertyMetas.Add(pmeta);
            }
            return(typeMeta);
        }