Next attempt. Did first 3 types.

src/Qowaiv/Date.cs

@@ -10,6 +10,9 @@
 [System.Text.Json.Serialization.JsonConverter(typeof(Json.DateJsonConverter))]
 #endif
 public readonly partial struct Date : ISerializable, IXmlSerializable, IFormattable, IEquatable<Date>, IComparable, IComparable<Date>
+#if NET6_0_OR_GREATER
+    , ISpanFormattable
+#endif
 #if NET7_0_OR_GREATER
     , IIncrementOperators<Date>, IDecrementOperators<Date>
     , IAdditionOperators<Date, TimeSpan, Date>, ISubtractionOperators<Date, TimeSpan, Date>
@@ -412,7 +415,17 @@ public string ToString(string? format, IFormatProvider? formatProvider)
             : m_Value.ToString(format, formatProvider);
     }
 
-    /// <summary>Gets an XML string representation of the @FullName.</summary>
+#if NET6_0_OR_GREATER
+    /// <inheritdoc />
+    public bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format, IFormatProvider? provider)
+    {
+        format = format.WithDefault("d");
+        return StringFormatter.TryApplyCustomFormatter(this, destination, out charsWritten, format, provider)
+            || m_Value.TryFormat(destination, out charsWritten, format, provider);
+    }
+#endif
+
+    /// <summary>Gets an XML string representation of the date.</summary>
     [Pure]
     private string ToXmlString() => ToString(SerializableFormat, CultureInfo.InvariantCulture);
 

src/Qowaiv/EmailAddressCollection.cs

@@ -333,7 +333,7 @@ public string ToString(string? format, IFormatProvider? formatProvider)
     /// s is not in the correct format.
     /// </exception>
     [Pure]
-    public static EmailAddressCollection Parse(string? s, IFormatProvider formatProvider)
+    public static EmailAddressCollection Parse(string? s, IFormatProvider? formatProvider)
     {
         if (TryParse(s, formatProvider, out EmailAddressCollection val))
         {

src/Qowaiv/Extensions/System.Span.cs

@@ -0,0 +1,45 @@
+#if NET6_0_OR_GREATER
+namespace System;
+
+internal static class QowaivSpanExtensions
+{
+    [Pure]
+    public static bool TryWrite(this Span<char> span, string? value, out int charsWritten)
+    {
+        if (value is { Length: > 0 })
+        {
+            if (value.TryCopyTo(span))
+            {
+                charsWritten = value.Length;
+                return true;
+            }
+            else
+            {
+                charsWritten = 0;
+                return false;
+            }
+        }
+        else
+        {
+            charsWritten = 0;
+            return true;
+        }
+    }
+
+    [Pure]
+    public static bool TryWrite(this Span<char> span, char ch, out int charsWritten)
+    {
+        if (span.Length != 0)
+        {
+            span.Fill(ch);
+            charsWritten = 1;
+            return true;
+        }
+        else
+        {
+            charsWritten = 0;
+            return false;
+        }
+    }
+}
+#endif

src/Qowaiv/Extensions/System.String.cs

@@ -66,6 +66,15 @@ public static string ToTitleCase(this string str, IFormatProvider provider)
     internal static string WithDefault(this string? str, string @default = "")
         => str is { Length: > 0 } ? str : @default;
 
+#if NET6_0_OR_GREATER
+    /// <summary>Returns the provided default if <see cref="string.IsNullOrEmpty(string)"/>,
+    /// otherwise the string value.
+    /// </summary>
+    [Pure]
+    internal static ReadOnlySpan<char> WithDefault(this ReadOnlySpan<char> str, ReadOnlySpan<char> @default)
+        => str.IsEmpty ? @default : str;
+#endif
+
     [Pure]
     internal static string Unify(this string? str) => str.Buffer().Unify();
 

src/Qowaiv/Financial/Amount.cs

@@ -12,6 +12,9 @@ namespace Qowaiv.Financial;
 [System.Text.Json.Serialization.JsonConverter(typeof(Json.Financial.AmountJsonConverter))]
 #endif
 public readonly partial struct Amount : ISerializable, IXmlSerializable, IFormattable, IEquatable<Amount>, IComparable, IComparable<Amount>
+#if NET6_0_OR_GREATER
+    , ISpanFormattable
+#endif
 #if NET7_0_OR_GREATER
     , IIncrementOperators<Amount>, IDecrementOperators<Amount>
     , IUnaryPlusOperators<Amount, Amount>, IUnaryNegationOperators<Amount, Amount>
@@ -393,6 +396,26 @@ namespace Qowaiv.Financial;
     [DebuggerBrowsable(DebuggerBrowsableState.Never)]
     private string DebuggerDisplay => this.DebuggerDisplay("¤{0:0.00########}");
 
+    /// <summary>Returns a formatted <see cref="string"/> that represents the current </summary>
+    /// <param name="format">
+    /// The format that describes the formatting.
+    /// </param>
+    /// <param name="formatProvider">
+    /// The format provider.
+    /// </param>
+    [Pure]
+    public string ToString(string? format, IFormatProvider? formatProvider)
+        => StringFormatter.TryApplyCustomFormatter(format, this, formatProvider, out string formatted)
+        ? formatted
+        : m_Value.ToString(format, Money.GetNumberFormatInfo(formatProvider));
+
+#if NET6_0_OR_GREATER
+    /// <inheritdoc />
+    public bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format, IFormatProvider? provider)
+        => StringFormatter.TryApplyCustomFormatter(this, destination, out charsWritten, format, provider)
+        || m_Value.TryFormat(destination, out charsWritten, format, Money.GetNumberFormatInfo(provider));
+#endif
+
     /// <summary>Gets an XML string representation of the amount.</summary>
     [Pure]
     private string ToXmlString() => ToString(CultureInfo.InvariantCulture);

src/Qowaiv/Financial/BusinessIdentifierCode.cs

@@ -30,6 +30,9 @@ namespace Qowaiv.Financial;
 [System.Text.Json.Serialization.JsonConverter(typeof(Json.Financial.BusinessIdentifierCodeJsonConverter))]
 #endif
 public readonly partial struct BusinessIdentifierCode : ISerializable, IXmlSerializable, IFormattable, IEquatable<BusinessIdentifierCode>, IComparable, IComparable<BusinessIdentifierCode>
+#if NET6_0_OR_GREATER
+    , ISpanFormattable
+#endif
 {
     /// <remarks>
     /// http://www.codeproject.com/KB/recipes/bicRegexValidator.aspx
@@ -96,6 +99,17 @@ public string ToString(string? format, IFormatProvider? formatProvider)
         else return m_Value ?? string.Empty;
     }
 
+#if NET6_0_OR_GREATER
+    /// <inheritdoc />
+    public bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format, IFormatProvider? provider)
+    {
+        if (StringFormatter.TryApplyCustomFormatter(this, destination, out charsWritten, format, provider)) return true;
+        else if (IsUnknown()) return destination.TryWrite('?', out charsWritten);
+        else return destination.TryWrite(m_Value, out charsWritten);
+    }
+
+#endif
+
     /// <summary>Gets an XML string representation of the BIC.</summary>
     [Pure]
     private string ToXmlString() => ToString(CultureInfo.InvariantCulture);

src/Qowaiv/Formatting/StringFormatter.cs

@@ -1,4 +1,7 @@
-namespace Qowaiv.Formatting;
+using Microsoft.VisualBasic;
+using System.ComponentModel;
+
+namespace Qowaiv.Formatting;
 
 /// <summary>A string formatter class.</summary>
 public static class StringFormatter
@@ -128,6 +131,41 @@ public static bool TryApplyCustomFormatter(string? format, object obj, IFormatPr
         }
     }
 
+#if NET6_0_OR_GREATER
+
+    /// <summary>Tries to apply the custom formatter to format the object.</summary>
+    /// <param name="obj">
+    /// The object to format.
+    /// </param>
+    /// <param name="destination">
+    /// The span in which to write this instance's value formatted as a span of characters.
+    /// </param>
+    /// <param name="format">
+    /// The format to apply
+    /// </param>
+    /// <param name="charsWritten">
+    /// When this method returns, contains the number of characters that were written in destination.
+    /// </param>
+    /// <param name="provider">
+    /// The format provider.
+    /// </param>
+    /// <returns>
+    /// True, if the format provider supports custom formatting, otherwise false.
+    /// </returns>
+    public static bool TryApplyCustomFormatter(object obj, Span<char> destination, out int charsWritten, ReadOnlySpan<char> format, IFormatProvider? provider)
+    {
+        if (TryApplyCustomFormatter(format.ToString(), obj, provider, out var formatted))
+        {
+            return destination.TryWrite(formatted, out charsWritten);
+        }
+        else
+        {
+            charsWritten = 0;
+            return false;
+        }
+    }
+#endif
+
     /// <summary>Replaces diacritic characters by non diacritic ones.</summary>
     /// <param name="str">
     /// The string to remove the diacritics from.