IFormattable에는 사용할 수있는 형식 공급자도 포함되어 있으며 dotnet 4.0에서는 IFormatProvider의 두 형식이 모두 null 일 수 있습니다.
/// <summary>
/// Extentionclass for a nullable structs
/// </summary>
public static class NullableStructExtensions {
/// <summary>
/// Formats a nullable struct
/// </summary>
/// <param name="source"></param>
/// <param name="format">The format string
/// If <c>null</c> use the default format defined for the type of the IFormattable implementation.</param>
/// <param name="provider">The format provider
/// If <c>null</c> the default provider is used</param>
/// <param name="defaultValue">The string to show when the source is <c>null</c>.
/// If <c>null</c> an empty string is returned</param>
/// <returns>The formatted string or the default value if the source is <c>null</c></returns>
public static string ToString<T>(this T? source, string format = null,
IFormatProvider provider = null,
string defaultValue = null)
where T : struct, IFormattable {
return source.HasValue
? source.Value.ToString(format, provider)
: (String.IsNullOrEmpty(defaultValue) ? String.Empty : defaultValue);
}
}
명명 된 매개 변수와 함께 사용하면 다음을 수행 할 수 있습니다.
dt2.ToString (defaultValue : "n / a");
이전 버전의 닷넷에서는 많은 과부하가 발생합니다.
/// <summary>
/// Extentionclass for a nullable structs
/// </summary>
public static class NullableStructExtensions {
/// <summary>
/// Formats a nullable struct
/// </summary>
/// <param name="source"></param>
/// <param name="format">The format string
/// If <c>null</c> use the default format defined for the type of the IFormattable implementation.</param>
/// <param name="provider">The format provider
/// If <c>null</c> the default provider is used</param>
/// <param name="defaultValue">The string to show when the source is <c>null</c>.
/// If <c>null</c> an empty string is returned</param>
/// <returns>The formatted string or the default value if the source is <c>null</c></returns>
public static string ToString<T>(this T? source, string format,
IFormatProvider provider, string defaultValue)
where T : struct, IFormattable {
return source.HasValue
? source.Value.ToString(format, provider)
: (String.IsNullOrEmpty(defaultValue) ? String.Empty : defaultValue);
}
/// <summary>
/// Formats a nullable struct
/// </summary>
/// <param name="source"></param>
/// <param name="format">The format string
/// If <c>null</c> use the default format defined for the type of the IFormattable implementation.</param>
/// <param name="defaultValue">The string to show when the source is null. If <c>null</c> an empty string is returned</param>
/// <returns>The formatted string or the default value if the source is <c>null</c></returns>
public static string ToString<T>(this T? source, string format, string defaultValue)
where T : struct, IFormattable {
return ToString(source, format, null, defaultValue);
}
/// <summary>
/// Formats a nullable struct
/// </summary>
/// <param name="source"></param>
/// <param name="format">The format string
/// If <c>null</c> use the default format defined for the type of the IFormattable implementation.</param>
/// <param name="provider">The format provider (if <c>null</c> the default provider is used)</param>
/// <returns>The formatted string or an empty string if the source is <c>null</c></returns>
public static string ToString<T>(this T? source, string format, IFormatProvider provider)
where T : struct, IFormattable {
return ToString(source, format, provider, null);
}
/// <summary>
/// Formats a nullable struct or returns an empty string
/// </summary>
/// <param name="source"></param>
/// <param name="format">The format string
/// If <c>null</c> use the default format defined for the type of the IFormattable implementation.</param>
/// <returns>The formatted string or an empty string if the source is null</returns>
public static string ToString<T>(this T? source, string format)
where T : struct, IFormattable {
return ToString(source, format, null, null);
}
/// <summary>
/// Formats a nullable struct
/// </summary>
/// <param name="source"></param>
/// <param name="provider">The format provider (if <c>null</c> the default provider is used)</param>
/// <param name="defaultValue">The string to show when the source is <c>null</c>. If <c>null</c> an empty string is returned</param>
/// <returns>The formatted string or the default value if the source is <c>null</c></returns>
public static string ToString<T>(this T? source, IFormatProvider provider, string defaultValue)
where T : struct, IFormattable {
return ToString(source, null, provider, defaultValue);
}
/// <summary>
/// Formats a nullable struct or returns an empty string
/// </summary>
/// <param name="source"></param>
/// <param name="provider">The format provider (if <c>null</c> the default provider is used)</param>
/// <returns>The formatted string or an empty string if the source is <c>null</c></returns>
public static string ToString<T>(this T? source, IFormatProvider provider)
where T : struct, IFormattable {
return ToString(source, null, provider, null);
}
/// <summary>
/// Formats a nullable struct or returns an empty string
/// </summary>
/// <param name="source"></param>
/// <returns>The formatted string or an empty string if the source is <c>null</c></returns>
public static string ToString<T>(this T? source)
where T : struct, IFormattable {
return ToString(source, null, null, null);
}
}