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Object Validation

DbEntry provides the validation feature for object model based on the information of itself.

For example, if a field do not mark by AllowNull attribute and not a nullable type object, and the value of it is null, the validate function will return false and the field name.

Another example, if a string field mark by Length with 8, and the real length of it is 10, the validate function will return false and the field name.

The validate function check all members of the object, if all passed, it will return true, if any check failed, it will return false.

The validate function belongs to ValidataHandler and named ValidateObject, it returns bool to tell us the basic result. The ValidateHandler has the property ErrorMessages. It’s a list of all failed message with fields name. We can show it to the end user if we want. The ValidateHandler also has a field named IsValid, it can gives use the bool result if we miss the return value of ValidateObject.

The arguments of constructor will let us define some acts of the validate function. EmptyAsNull means the empty string will regarded as null, if the value is get from user input, it will not be null, so this argument makes us can check this situation. NotNullFieldMinSize makes us can check the min length of the not null string field, normally it will set to 1. IncludeClassName means the error message of field name will include class name. InvalidFieldText makes us can set the invalid text by ourselves.

The AllowNull will check all types of the field. And Length, StringColumn will check string type field only. StringColumn include isUnicode and Reguar checks all.

The attributes not only works for validate, but also works for create table.

The following code is a simple sample of object definition:

class vtest : IDbObject
    [Length(5), StringColumn(IsUnicode=false)]
    public string Name;

    [AllowNull, Length(8)]
    public string Address;

    public string Email;

    public vtest() { }

    public vtest(string Name, string Address, string Email)
        this.Name = Name;
        this.Address = Address;
        this.Email = Email;

And the usage of ValidateHandler:

ValidateHandler vh = new ValidateHandler(true, 1);
vh.ValidateObject(new vtest("12345", null, "a@b.c")); // true
vh.ValidateObject(new vtest("123456", null, "a@b.c")); // false
vh.ValidateObject(new vtest("", null, "a@b.c")); // false
vh.ValidateObject(new vtest("1", null, "a@b.c")); // true
vh.ValidateObject(new vtest("1", null, "a@b@c")); // false

Last edited Apr 9, 2014 at 3:01 PM by lifeng, version 8


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