trouble with changing default behavior for nullable column get in dataset

问题

default column get for a dataRow in .designer.cs is like

    public partial class Fi_securityRow : global::System.Data.DataRow
{
    [global::system.diagnostics.debuggernonusercodeattribute()]
    [global::System.CodeDom.Compiler.GeneratedCodeAttribute("System.Data.Design.TypedDataSetGenerator", "4.0.0.0")]
    public override System.DateTime Exp_dt
    {
        get
        {
            try
            {
                return ((global::System.DateTime)(this[this.tableFi_security.Exp_dtColumn]));
            }
            catch (global::System.InvalidCastException e)
            {
                throw new global::System.Data.StrongTypingException("The value for column \'Exp_dt\' in table \'Fi_security\' is DBNull.", e);
            }
        }
        set
        {
            this[this.tableFi_security.Exp_dtColumn] = value;
        }
    }
}

when I tried to change that behavior by adding in .cs file in the dataset class

public partial class IeFinExecPDataSet
{
    public partial class Fi_securityDataTable
    {

        /// <summary> line 19938
        ///Represents strongly named DataRow class.
        ///</summary>
        public partial class Fi_securityRow : global::System.Data.DataRow
        {
            [global::System.Diagnostics.DebuggerNonUserCodeAttribute()]
            [global::System.CodeDom.Compiler.GeneratedCodeAttribute("System.Data.Design.TypedDataSetGenerator", "4.0.0.0")]
            public override System.DateTime? Exp_dt
            {
                get
                {
                    try
                    {
                    if (this[this.tableFi_security.Exp_dtColumn]==System.DBNull.Value) return null;
                        return ((global::System.DateTime)(this[this.tableFi_security.Exp_dtColumn]));
                    }
                    catch (global::System.InvalidCastException e)
                    {
                        throw new global::System.Data.StrongTypingException("The value for column \'Exp_dt\' in table \'Fi_security\' is DBNull.", e);
                    }
                }
                set
                {
                    this[this.tableFi_security.Exp_dtColumn] = value;
                }
            }
        }
    }
}

I get Error 12 'mynamespace.ADataSet.Fi_securityDataTable.Fi_securityRow.Exp_dt': no suitable method found to override ...

where did I go wrong?

回答1:

You're going about this all wrong. DO NOT edit the generated code. If you want a property that is type DateTime? then add an extra partial class with an extra property of that type. You might implement that property like this:

public DateTime? NullableExp_dt
{
    get
    {
        if (this.IsExp_dtNull())
        {
            return (DateTime?) null;
        }
        else
        {
            return (DateTime?) this.Exp_dt;
        }
    }
    set
    {
        if (value.HasValue())
        {
            this.Exp_dt = value.Value;
        }
        else
        {
            this.SetExp_dtNull();
        }
    }
}

来源：https://stackoverflow.com/questions/25860241/trouble-with-changing-default-behavior-for-nullable-column-get-in-dataset