Add project files.

MyOffice.Core/Extensions/StringExtensions.cs

@@ -0,0 +1,29 @@
+namespace MyOffice.Core.Extensions;
+
+public static class StringExtensions
+{
+	public static bool IsMissing(this string? str)
+	{
+		return str == null || string.IsNullOrEmpty(str) || string.IsNullOrEmpty(str.Trim());
+	}
+
+	public static bool IsPresent(this string? str)
+	{
+		return !IsMissing(str);
+	}
+
+	public static string? NullIfEmpty(this string? str)
+	{
+		return IsMissing(str) ? null : str;
+	}
+
+	public static bool EqualsIgnoreCase(this string? str, string? value)
+	{
+		return str != null && str.Equals(value, StringComparison.OrdinalIgnoreCase);
+	}
+
+	public static bool AsBool(this string? str, bool defaultValue = false)
+	{
+		return true.ToString().Equals(str, StringComparison.OrdinalIgnoreCase) || defaultValue;
+	}
+}