ValidationViewModelBase.cs

Language: C#
Last Modified: 2020-06-27 1:58:36 PM UTC
File Size: 2718 bytes

http://www.penguinstew.ca/example/MVVMbase/ViewModelBase/ValidationViewModelBase.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.ComponentModel;

namespace Penguin.MVVMBase.ViewModelBase

{

/// <summary>

/// Base for ViewModel with Validation

/// </summary>

public class ValidationViewModelBase : ViewModelBase, IDataErrorInfo

{

#region Fields

/// <summary>

/// Dictionary of validation functions mapped to property names

/// </summary>

private Dictionary<string, Func<string>> m_validationFunctions = new Dictionary<string, Func<string>>();

#endregion

#region IDataErrorInfo

/// <summary>

/// Returns an error message for the whole view model

/// </summary>

public string Error

{

get { return String.Empty; }

}

/// <summary>

/// Returns error message for the given item

/// </summary>

/// <param name="columnName">The item to validate</param>

/// <returns>Empty string if valid, error message otherwise</returns>

public string this[string columnName]

{

get {

Func<string> validationFunction;

if (m_validationFunctions.TryGetValue(columnName, out validationFunction))

{

return validationFunction();

}

else

{

return string.Empty;

}

#endregion

/// <summary>

/// Tests if all properties on this view model are valid

/// </summary>

/// <returns>True if valid, false otherwise</returns>

protected bool IsValid()

{

bool isValid = m_validationFunctions.All(v => String.IsNullOrEmpty(v.Value()));

return isValid;

}

/// <summary>

/// Adds the given validation function for the given property

/// </summary>

/// <param name="propertyName">Name of the property being validated</param>

/// <param name="validationFunction">The function to validate the property</param>

protected void AddValidation(string propertyName, Func<string> validationFunction)

{

//Test propertyName to make sure it's a valid property

if (TypeDescriptor.GetProperties(this)[propertyName] == null)

{

string msg = "Invalid property name: " + propertyName;

throw new ArgumentException(msg);

}

m_validationFunctions.Add(propertyName, validationFunction);

}