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POHow to provide validation for child classes that implement different properties?
 

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  1. POHow to provide validation for child classes that implement different properties?
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    <p>I have a parent class implementing INotifyPropertyChanged, and the parent class has multiple children. The children have different properties that all call PropertyChanged. I want to add validation, but I really don't want to have to write validations for every child class. The validation rules are supplied from the database, so I would have to eventually pull the validation rules for each child, then check the value against the rules. If I did that, I think that it would have too much redundant code, and I would like to have it placed at the parent level since PropertyChanged triggers on the string value of the value itself. </p> <p>Is it possible to have the validation method on the parent class so I wouldn't have to write a validation method for every child class? Mind you, the properties in every child class are different.</p> <p>Below is what I currently have, with validation in the child class.</p> <pre><code>public Parent : INotifyChanged { /// &lt;summary&gt; /// Occurs when a property is changed /// &lt;/summary&gt; public event PropertyChangedEventHandler PropertyChanged; /// &lt;summary&gt; /// Raises the &lt;see cref="PropertyChanged"/&gt; for a given /// property. /// &lt;/summary&gt; /// &lt;param name="propertyName"&gt;&lt;/param&gt; protected void OnPropertyChanged(String propertyName) { // Get the hanlder PropertyChangedEventHandler handler = this.PropertyChanged; // Check that the event handler is not null if(null != handler) { // Fire the event handler(this, new PropertyChangedEventArgs(propertyName)); } } } </code></pre> <p>Child1 Class:</p> <pre><code>public Child1 : Parent, IDataErrorInfo { private Dictionary&lt;string, string&gt; m_validationErrors = new Dictionary&lt;string, string&gt;(); private void Validate() { this.RemoveError("Child1Description"); if(!Regex.IsMatch(Child1Description, "^([a-zA-Z '-]+)$") &amp;&amp; !String.IsNullOrWhiteSpace(Description)) { this.AddError("Child1Description", "Only non-numerics allowed."); } } private void AddError(string columnName, string msg) { if(!m_validationErrors.ContainsKey(columnName)) { m_validationErrors.Add(columnName, msg); } } private void RemoveError(string columnName) { if(m_validationErrors.ContainsKey(columnName)) { m_validationErrors.Remove(columnName); } } public string Error { get { if(m_validationErrors.Count &gt; 0) { return "Field data is invalid."; } else return null; } } public string this[string columnName] { get { if(m_validationErrors.ContainsKey(columnName)) { return m_validationErrors[columnName]; } else { return null; } } } /// &lt;summary&gt; /// Description of the air entity /// &lt;/summary&gt; public string Child1Description { get { return Child1description; } set { description = value; Validate(); OnPropertyChanged("Child1Description"); } } } </code></pre> <p>Child2 Class:</p> <pre><code>public Child2 : Parent, IDataErrorInfo { private Dictionary&lt;string, string&gt; m_validationErrors = new Dictionary&lt;string, string&gt;(); private void Validate() { this.RemoveError("Child2Description"); if(!Regex.IsMatch(Child2Description, "^([a-zA-Z '-]+)$") &amp;&amp; !String.IsNullOrWhiteSpace(Description)) { this.AddError("Child2Description", "Only non-numerics allowed."); } } private void AddError(string columnName, string msg) { if(!m_validationErrors.ContainsKey(columnName)) { m_validationErrors.Add(columnName, msg); } } private void RemoveError(string columnName) { if(m_validationErrors.ContainsKey(columnName)) { m_validationErrors.Remove(columnName); } } public string Error { get { if(m_validationErrors.Count &gt; 0) { return "Field data is invalid."; } else return null; } } public string this[string columnName] { get { if(m_validationErrors.ContainsKey(columnName)) { return m_validationErrors[columnName]; } else { return null; } } } /// &lt;summary&gt; /// Description of the air entity /// &lt;/summary&gt; public string Child2Description { get { return Child2description; } set { description = value; Validate(); OnPropertyChanged("Child2Description"); } } } </code></pre>
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    1. COQ: Is it possible to have the validation method on the parent class? A: Sure. Why not? What exactly is your question? Can you post any code?
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    2. CO@paulsm4 Sorry, was trying to clean it up. Code added.
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