wpf datagrid中绑定十进制值的问题

还有一个wpf问题

我有两个DataGridTextColumn，它们接受十进制值。出于某种原因，当我添加新行（列的初始值为零）时，我必须在这两列中的任何一列中输入两次值。我第一次在其中键入值并进行制表时，该值返回到零。在我第二次输入值后，它将保持不变

<DataGridTextColumn Header="Unit Price" EditingElementStyle="{StaticResource CellEditStyle}" Width="SizeToCells" MinWidth="90" Binding="{Binding ItemUnitPrice, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True}" />
<DataGridTextColumn Header="Qty" EditingElementStyle="{StaticResource CellEditStyle}" Width="SizeToCells" MinWidth="65" Binding="{Binding ItemQty, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True}" />

---

}

从技术上讲，这不是一个答案，但我发现问题如下：

        if (propertyName == "ItemQty") 
        { 
            if (this.ItemQty == 0.0M) 
                result = "Item quantity cannot be empty!"; 
        }

由于dg列的默认值为零，因此这在新行上总是失败的。一旦我摆脱了这张支票，问题就消失了

但是，我也有一个必填字段的问题。输入新行后，验证过程（IDataError）将立即启动。显然，大多数验证都会失败，因为您还没有输入数据。但是，当您输入初始值时，即使它是合法的，该值也会被清除。我认为这不是正确的行为，我想知道是否有办法在用户离开datagrid行之前关闭初始验证。除此之外，我不知道为什么它会被清除。它仅在输入初始值时发生。一旦你签出并返回，你可以输入一个值，它将保持它，有效或无效。如果无效，验证样式将按其应有的方式标记无效列

public class ProjectExpenseItemsBO : IDataErrorInfo, IEditableObject
{
    public int RowID { get; set; }
    public int ProjectExpenseID { get; set; }
    public string ItemNumber { get; set; }
    public string ItemDescription { get; set; }
    public decimal ItemUnitPrice { get; set; }
    public decimal ItemQty { get; set; }
    public string SupplierName { get; set; }
    public DateTime CreateDate { get; set; }

    public ProjectExpenseItemsBO()
    {

    }
   // string method
    static bool IsStringMissing(string value)
    {
        return String.IsNullOrEmpty(value) || value.Trim() == String.Empty;
    }

    private bool _isValid = true;
    public bool IsValid 
    {
        get { return _isValid; }
        set { _isValid = value; }
    }

    #region IDataErrorInfo Members

    public string Error
    {
        get
        {
            return this[string.Empty];
        }
    }

    public string this[string propertyName]
    {
        get
        {
            string result = string.Empty;
            if (propertyName == "ProjectExpenseID")
            {
                if (this.ProjectExpenseID == 0)
                    result = "An existing project expense item must be selected!";
            }

            if (propertyName == "ItemNumber")
            {
                if (this.ItemNumber != null)
                {
                    if (IsStringMissing(this.ItemNumber))
                        result = "Item number cannot be empty!";
                    if (this.ItemNumber.Length > 50)
                        result = "Item number cannot be longer than 50 characters!";
                }
            }

            if (propertyName == "ItemDescription")
            {
                if (this.ItemDescription != null)
                {
                    if (this.ItemDescription.Length > 256)
                        result = "Item description cannot be longer than 256 characters!";
                }
            }

            if (propertyName == "ItemUnitPrice")
            {
                if (this.ItemUnitPrice == 0.0M)
                    result = "Item unit price cannot be empty!";
            }

            if (propertyName == "ItemQty")
            {
                if (this.ItemQty == 0.0M)
                    result = "Item quantity cannot be empty!";
            }

            if (propertyName == "SupplierName")
            {
                if (this.SupplierName != null)
                {
                    if (this.SupplierName.Length > 128)
                        result = "Item number cannot be longer than 128 characters!";
                }
            }

            if (result.Length > 0)
                IsValid = false;
            else
                IsValid = true;

            return result;
        }
    }

    #endregion

    #region IEditableObject Members

    public delegate void ItemEndEditEventHandler(IEditableObject sender);

    public event ItemEndEditEventHandler ItemEndEdit;

    public void BeginEdit()
    {
        //throw new NotImplementedException();
    }

    public void CancelEdit()
    {
        //throw new NotImplementedException();
    }

    public void EndEdit()
    {
        if (ItemEndEdit != null)
        {
            ItemEndEdit(this);
        }
    }

    #endregion
}

        if (propertyName == "ItemQty") 
        { 
            if (this.ItemQty == 0.0M) 
                result = "Item quantity cannot be empty!"; 
        }