Question

正如你可能从标题中看到的那样，我将要问一些之前被问过很多次的事情。但是，在阅读了所有这些其他问题后，我找不到合适的解决方案来解决我的问题。

我有一个基本验证的模型类：

partial class Player : IDataErrorInfo
{
    public bool CanSave { get; set; }

    public string this[string columnName]
    {
        get 
        { 
            string result = null;
            if (columnName == "Firstname")
            {
                if (String.IsNullOrWhiteSpace(Firstname))
                {
                    result = "Geef een voornaam in";
                }
            }
            if (columnName == "Lastname")
            {
                if (String.IsNullOrWhiteSpace(Lastname))
                {
                    result = "Geef een familienaam in";
                }
            }
            if (columnName == "Email")
            {
                try
                {
                    MailAddress email = new MailAddress(Email);
                }
                catch (FormatException)
                {
                    result = "Geef een geldig e-mailadres in";
                }
            }
            if (columnName == "Birthdate")
            {
                if (Birthdate.Value.Date >= DateTime.Now.Date)
                {
                    result = "Geef een geldige geboortedatum in";
                }
            }

            CanSave = true; // this line is wrong
            return result;
        }
    }

    public string Error { get { throw new NotImplementedException();} }
}

每次属性更改时都会进行此验证（因此每次用户在文本框中键入一个字符时）：

<TextBox Text="{Binding CurrentPlayer.Firstname, ValidatesOnDataErrors=True, UpdateSourceTrigger=PropertyChanged}" VerticalAlignment="Top" Width="137" IsEnabled="{Binding Editing}" Grid.Row="1"/>

这很完美。验证发生（绑定的PropertyChanged代码在CurrentPlayer属性上的VM中完成，该属性是Player的对象。）

我现在要做的是在验证失败时禁用保存按钮。

首先，最简单的解决方案似乎可以在这个帖子中找到：
Enable Disable save button during Validation using IDataErrorInfo

如果我想遵循公认的解决方案，我必须写下我的验证码两次，因为我不能简单地使用索引器。写作双重代码绝对不是我想要的，所以这不是解决方案我的问题。
关于那个帖子的第二个答案听起来很有希望作为第一个，但问题是我必须有多个字段验证。这样，一切都依赖于最后一次检查的财产（如果正确填写该字段，CanSave将是真的，甚至虽然还有其他字段仍无效）。

我发现的另一个解决方案是使用ErrorCount属性。但是，由于我在每次更改属性时都会进行验证（对每个类型的角色也是如此），这也是不可能的 - 我怎么知道何时增加/减少ErrorCount？

解决此问题的最佳方法是什么？

由于

Answer 1

本文http://www.asp.net/mvc/tutorials/older-versions/models-%28data%29/validating-with-the-idataerrorinfo-interface-cs将个人验证移至属性中：

public partial class Player : IDataErrorInfo
{
    Dictionary<string, string> _errorInfo;

    public Player()
    {
        _errorInfo = new Dictionary<string, string>();
    }

    public bool CanSave { get { return _errorInfo.Count == 0; }

    public string this[string columnName]
    {
        get 
        { 
            return _errorInfo.ContainsKey(columnName) ? _errorInfo[columnName] : null;
        }
    }

    public string FirstName
    {
        get { return _firstName;}
        set
        {
            if (String.IsNullOrWhiteSpace(value))
                _errorInfo.AddOrUpdate("FirstName", "Geef een voornaam in");
            else
            {
                _errorInfo.Remove("FirstName");
                _firstName = value;
            }
        }
    }
}

（您必须处理Dictionary AddOrUpdate扩展方法）。这类似于错误计数的想法。

Answer 2

我已经实现了my comment above中显示的地图方法，在C＃中，这称为Dictionary我在其中使用anonymous methods进行验证：

partial class Player : IDataErrorInfo
{
    private delegate string Validation(string value);
    private Dictionary<string, Validation> columnValidations;
    public List<string> Errors;

    public Player()
    {
        columnValidations = new Dictionary<string, Validation>();
        columnValidations["Firstname"] = delegate (string value) {
            return String.IsNullOrWhiteSpace(Firstname) ? "Geef een voornaam in" : null;
        }; // Add the others...

        errors = new List<string>();
    }

    public bool CanSave { get { return Errors.Count == 0; } }

    public string this[string columnName]
    {
        get { return this.GetProperty(columnName); } 

        set
        { 
            var error = columnValidations[columnName](value);

            if (String.IsNullOrWhiteSpace(error))
                errors.Add(error);
            else
                this.SetProperty(columnName, value);
        }
    }
}

Answer 3

此方法适用于数据注释。您还可以将“IsValid”属性绑定到“保存”按钮以启用/禁用。

public abstract class ObservableBase : INotifyPropertyChanged, IDataErrorInfo
{
    #region Members
    private readonly Dictionary<string, string> errors = new Dictionary<string, string>();
    #endregion

    #region Events

    /// <summary>
    /// Property Changed Event
    /// </summary>
    public event PropertyChangedEventHandler PropertyChanged;

    #endregion

    #region Protected Methods

    /// <summary>
    /// Get the string name for the property
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="expression"></param>
    /// <returns></returns>
    protected string GetPropertyName<T>(Expression<Func<T>> expression)
    {
        var memberExpression = (MemberExpression) expression.Body;
        return memberExpression.Member.Name;
    }

    /// <summary>
    /// Notify Property Changed (Shorted method name)
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="expression"></param>
    protected virtual void Notify<T>(Expression<Func<T>> expression)
    {
        string propertyName = this.GetPropertyName(expression);
        PropertyChangedEventHandler handler = this.PropertyChanged;
        handler?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }

    /// <summary>
    /// Called when [property changed].
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="expression">The expression.</param>
    protected virtual void OnPropertyChanged<T>(Expression<Func<T>> expression)
    {
        string propertyName = this.GetPropertyName(expression);
        PropertyChangedEventHandler handler = this.PropertyChanged;

        handler?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }

    #endregion

    #region Properties

    /// <summary>
    /// Gets an error message indicating what is wrong with this object.
    /// </summary>
    public string Error => null;

    /// <summary>
    /// Returns true if ... is valid.
    /// </summary>
    /// <value>
    ///   <c>true</c> if this instance is valid; otherwise, <c>false</c>.
    /// </value>
    public bool IsValid => this.errors.Count == 0;

    #endregion

    #region Indexer

    /// <summary>
    /// Gets the <see cref="System.String"/> with the specified column name.
    /// </summary>
    /// <value>
    /// The <see cref="System.String"/>.
    /// </value>
    /// <param name="columnName">Name of the column.</param>
    /// <returns></returns>
    public string this[string columnName]
    {
        get
        {
            var validationResults = new List<ValidationResult>();
            string error = null;

            if (Validator.TryValidateProperty(GetType().GetProperty(columnName).GetValue(this), new ValidationContext(this) { MemberName = columnName }, validationResults))
            {
                this.errors.Remove(columnName);
            }
            else
            {
                error = validationResults.First().ErrorMessage;

                if (this.errors.ContainsKey(columnName))
                {
                    this.errors[columnName] = error;
                }
                else
                {
                    this.errors.Add(columnName, error);
                }
            }

            this.OnPropertyChanged(() => this.IsValid);
            return error;
        }
    }

    #endregion  
}

验证失败时禁用保存按钮

3 个答案: