Added base files.

Author: CodingMadeEasy

C9S.Extensions.Configuration.sln

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+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio 15
+VisualStudioVersion = 15.0.26124.0
+MinimumVisualStudioVersion = 15.0.26124.0
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Debug|x64 = Debug|x64
+		Debug|x86 = Debug|x86
+		Release|Any CPU = Release|Any CPU
+		Release|x64 = Release|x64
+		Release|x86 = Release|x86
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+EndGlobal

C9S.Extensions.Configuration/C9S.Extensions.Configuration.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>netstandard2.0</TargetFramework>
+  </PropertyGroup>
+
+</Project>

C9S.Extensions.Configuration/ConfigurationRootExtensions.cs

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+using System;
+
+namespace C9S.Extensions.Configuration
+{
+    public static class ConfigurationRootExtensions
+    {
+        public static void ResolveVariables(this IConfigurationRoot configuration)
+        {
+            foreach (var configSection in configuration.GetChildren())
+            {
+                foreach (Match match in variableRegex.Matches(configSection.Value ?? ""))
+                {
+                    var variable = match.Groups["var"].Value;
+                    var sections = new List<string>(variable.Split('.', System.StringSplitOptions.RemoveEmptyEntries));
+                    IConfigurationSection section = configSection;
+                    if (sections.Any())
+                    {
+                        section = Configuration.GetSection(sections[0]);
+                        var key = sections.Last();
+
+                        sections.RemoveAt(0);
+                        sections.RemoveAt(sections.Count - 1);
+                        foreach (var sec in sections)
+                        {
+                            section = section.GetSection(sec);
+                        }
+
+                        configSection.Value = configSection.Value.Replace($"{{{{{variable}}}}}", section[key]);
+                    }
+                }
+
+                ResolveVariables(configSection);
+            }
+        }
+    }
+}