diff --git a/config.json b/config.json
index 0421ce0a34..6fefb0094e 100644
--- a/config.json
+++ b/config.json
@@ -1240,6 +1240,30 @@
       ],
       "unlocked_by": "markdown",
       "uuid": "a5794706-58d2-48f7-8aab-78639d7bce77"
+    },
+    {
+      "core": false,
+      "deprecated": true,
+      "slug": "binary",
+      "uuid": "cef7deef-54ce-4201-b263-7cd2098533f8"
+    },
+    {
+      "core": false,
+      "deprecated": true,
+      "slug": "trinary",
+      "uuid": "c7dd8467-87e2-4997-a96e-a04cb8b891e8"
+    },
+    {
+      "core": false,
+      "deprecated": true,
+      "slug": "octal",
+      "uuid": "c8555f37-9976-4f52-a5db-6a680ec8d53b"
+    },
+    {
+      "core": false,
+      "deprecated": true,
+      "slug": "hexadecimal",
+      "uuid": "5d30c5a0-0f69-4b79-8c7e-3b1fe6a5707f"
     }
   ],
   "foregone": [
diff --git a/exercises/binary/Binary.cs b/exercises/binary/Binary.cs
new file mode 100644
index 0000000000..7520799eb6
--- /dev/null
+++ b/exercises/binary/Binary.cs
@@ -0,0 +1,9 @@
+using System;
+
+public class Binary
+{
+    public static int ToDecimal(string binary)
+    {
+        throw new NotImplementedException("You need to implement this function.");
+    }
+}
diff --git a/exercises/binary/Binary.csproj b/exercises/binary/Binary.csproj
new file mode 100644
index 0000000000..082b3bbe5f
--- /dev/null
+++ b/exercises/binary/Binary.csproj
@@ -0,0 +1,17 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>netcoreapp2.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Remove="Example.cs" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.5.0" />
+    <PackageReference Include="xunit" Version="2.3.1" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.3.1" />
+  </ItemGroup>
+
+</Project>
diff --git a/exercises/binary/BinaryTest.cs b/exercises/binary/BinaryTest.cs
new file mode 100644
index 0000000000..28b2e01d32
--- /dev/null
+++ b/exercises/binary/BinaryTest.cs
@@ -0,0 +1,94 @@
+using Xunit;
+
+public class BinaryTest
+{
+    [Fact]
+    public void Binary_0_is_decimal_0()
+    {
+        Assert.Equal(0, Binary.ToDecimal("0"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Binary_1_is_decimal_1()
+    {
+        Assert.Equal(1, Binary.ToDecimal("1"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Binary_10_is_decimal_2()
+    {
+        Assert.Equal(2, Binary.ToDecimal("10"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Binary_11_is_decimal_3()
+    {
+        Assert.Equal(3, Binary.ToDecimal("11"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Binary_100_is_decimal_4()
+    {
+        Assert.Equal(4, Binary.ToDecimal("100"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Binary_1001_is_decimal_9()
+    {
+        Assert.Equal(9, Binary.ToDecimal("1001"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Binary_11010_is_decimal_26()
+    {
+        Assert.Equal(26, Binary.ToDecimal("11010"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Binary_10001101000_is_decimal_1128()
+    {
+        Assert.Equal(1128, Binary.ToDecimal("10001101000"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Binary_ignores_leading_zeros()
+    {
+        Assert.Equal(31, Binary.ToDecimal("000011111"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Invalid_binary_2_converts_to_decimal_0()
+    {
+        Assert.Equal(0, Binary.ToDecimal("2"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void A_number_containing_a_non_binary_digit_is_invalid()
+    {
+        Assert.Equal(0, Binary.ToDecimal("01201"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void A_number_with_trailing_non_binary_characters_is_invalid()
+    {
+        Assert.Equal(0, Binary.ToDecimal("10nope"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void A_number_with_leading_non_binary_characters_is_invalid()
+    {
+        Assert.Equal(0, Binary.ToDecimal("nope10"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void A_number_with_internal_non_binary_characters_is_invalid()
+    {
+        Assert.Equal(0, Binary.ToDecimal("10nope10"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void A_number_and_a_word_whitespace_separated_is_invalid()
+    {
+        Assert.Equal(0, Binary.ToDecimal("001 nope"));
+    }
+}
diff --git a/exercises/binary/Example.cs b/exercises/binary/Example.cs
new file mode 100644
index 0000000000..5a16c88670
--- /dev/null
+++ b/exercises/binary/Example.cs
@@ -0,0 +1,24 @@
+using System;
+using System.Linq;
+
+public class Binary
+{
+    public static int ToDecimal(string binary)
+    {
+        if (IsNotValidBinary(binary)) return 0;
+
+        return binary
+            .Select((c, i) => int.Parse(c.ToString()) * TwoToThePowerOf(binary.Length - i - 1))
+            .Sum();
+    }
+
+    private static bool IsNotValidBinary(string binary)
+    {
+        return !binary.All(x => char.IsDigit(x) && int.Parse(x.ToString()) < 2);
+    }
+
+    private static int TwoToThePowerOf(int power)
+    {
+        return (int)Math.Pow(2, power);
+    }
+}
\ No newline at end of file
diff --git a/exercises/binary/README.md b/exercises/binary/README.md
new file mode 100644
index 0000000000..bdbc9169c2
--- /dev/null
+++ b/exercises/binary/README.md
@@ -0,0 +1,41 @@
+# Binary
+
+Convert a binary number, represented as a string (e.g. '101010'), to its decimal equivalent using first principles.
+
+Implement binary to decimal conversion. Given a binary input
+string, your program should produce a decimal output. The
+program should handle invalid inputs.
+
+## Note
+- Implement the conversion yourself.
+  Do not use something else to perform the conversion for you.
+
+## About Binary (Base-2)
+Decimal is a base-10 system.
+
+A number 23 in base 10 notation can be understood
+as a linear combination of powers of 10:
+
+- The rightmost digit gets multiplied by 10^0 = 1
+- The next number gets multiplied by 10^1 = 10
+- ...
+- The *n*th number gets multiplied by 10^*(n-1)*.
+- All these values are summed.
+
+So: `23 => 2*10^1 + 3*10^0 => 2*10 + 3*1 = 23 base 10`
+
+Binary is similar, but uses powers of 2 rather than powers of 10.
+
+So: `101 => 1*2^2 + 0*2^1 + 1*2^0 => 1*4 + 0*2 + 1*1 => 4 + 1 => 5 base 10`.
+
+### Submitting Exercises
+
+Note that, when trying to submit an exercise, make sure the exercise file that you're submitting is in the `exercism/csharp/<exerciseName>` directory.
+
+For example, if you're submitting `bob.cs` for the Bob exercise, the submit command would be something like `exercism submit <path_to_exercism_dir>/csharp/bob/bob.cs`.
+## Source
+
+All of Computer Science [http://www.wolframalpha.com/input/?i=binary&a=*C.binary-_*MathWorld-](http://www.wolframalpha.com/input/?i=binary&a=*C.binary-_*MathWorld-)
+
+## Submitting Incomplete Solutions
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.
diff --git a/exercises/hexadecimal/Example.cs b/exercises/hexadecimal/Example.cs
new file mode 100644
index 0000000000..01271d7dc7
--- /dev/null
+++ b/exercises/hexadecimal/Example.cs
@@ -0,0 +1,41 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text.RegularExpressions;
+
+public class Hexadecimal
+{
+    private static readonly Dictionary<char, int> AlphaValues = new Dictionary<char, int>
+        {
+            { 'a', 10 },
+            { 'b', 11 },
+            { 'c', 12 },
+            { 'd', 13 },
+            { 'e', 14 },
+            { 'f', 15 }
+        };
+
+    public static int ToDecimal(string value)
+    {
+        if (IsNotValidHexadecimal(value)) return 0;
+
+        return value.Select((c, i) => GetNumericValue(c) * SixteenToThePowerOf(value.Length - i - 1)).Sum();
+    }
+
+    private static bool IsNotValidHexadecimal(string value)
+    {
+        return Regex.IsMatch(value, "[^0-9abcdef]", RegexOptions.IgnoreCase);
+    }
+
+    private static int GetNumericValue(char value)
+    {
+        if (char.IsNumber(value))
+            return (int)char.GetNumericValue(value);
+        return AlphaValues[value];
+    }
+
+    private static int SixteenToThePowerOf(int power)
+    {
+        return (int)Math.Pow(16, power);
+    }
+}
\ No newline at end of file
diff --git a/exercises/hexadecimal/Hexadecimal.cs b/exercises/hexadecimal/Hexadecimal.cs
new file mode 100644
index 0000000000..090b4efb25
--- /dev/null
+++ b/exercises/hexadecimal/Hexadecimal.cs
@@ -0,0 +1,9 @@
+using System;
+
+public class Hexadecimal
+{
+    public static int ToDecimal(string value)
+    {
+        throw new NotImplementedException("You need to implement this function.");
+    }
+}
diff --git a/exercises/hexadecimal/Hexadecimal.csproj b/exercises/hexadecimal/Hexadecimal.csproj
new file mode 100644
index 0000000000..082b3bbe5f
--- /dev/null
+++ b/exercises/hexadecimal/Hexadecimal.csproj
@@ -0,0 +1,17 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>netcoreapp2.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Remove="Example.cs" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.5.0" />
+    <PackageReference Include="xunit" Version="2.3.1" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.3.1" />
+  </ItemGroup>
+
+</Project>
diff --git a/exercises/hexadecimal/HexadecimalTest.cs b/exercises/hexadecimal/HexadecimalTest.cs
new file mode 100644
index 0000000000..a708cc4064
--- /dev/null
+++ b/exercises/hexadecimal/HexadecimalTest.cs
@@ -0,0 +1,65 @@
+using Xunit;
+
+public class HexadecimalTest
+{
+    [Fact(Skip = "Remove to run test")]
+    public void Hexadecimal_1_is_decimal_1()
+    {
+        Assert.Equal(1, Hexadecimal.ToDecimal("1"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Hexadecimal_c_is_decimal_12()
+    {
+        Assert.Equal(12, Hexadecimal.ToDecimal("c"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Hexadecimal_10_is_decimal_16()
+    {
+        Assert.Equal(16, Hexadecimal.ToDecimal("10"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Hexadecimal_af_is_decimal_175()
+    {
+        Assert.Equal(175, Hexadecimal.ToDecimal("af"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Hexadecimal_100_is_decimal_256()
+    {
+        Assert.Equal(256, Hexadecimal.ToDecimal("100"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Hexadecimal_19ace_is_decimal_105166()
+    {
+        Assert.Equal(105166, Hexadecimal.ToDecimal("19ace"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Hexadecimal_carrot_is_decimal_0()
+    {
+        Assert.Equal(0, Hexadecimal.ToDecimal("carrot"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Hexadecimal_000000_is_decimal_0()
+    {
+        Assert.Equal(0, Hexadecimal.ToDecimal("000000"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Hexadecimal_ffffff_is_decimal_16777215()
+    {
+        Assert.Equal(16777215, Hexadecimal.ToDecimal("ffffff"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Hexadecimal_ffff00_is_decimal_16776960()
+    {
+        Assert.Equal(16776960, Hexadecimal.ToDecimal("ffff00"));
+    }
+
+}
diff --git a/exercises/hexadecimal/README.md b/exercises/hexadecimal/README.md
new file mode 100644
index 0000000000..98e239789f
--- /dev/null
+++ b/exercises/hexadecimal/README.md
@@ -0,0 +1,20 @@
+# Hexadecimal
+
+Convert a hexadecimal number, represented as a string (e.g. "10af8c"), to its decimal equivalent using first principles (i.e. no, you may not use built-in or external libraries to accomplish the conversion).
+
+On the web we use hexadecimal to represent colors, e.g. green: 008000,
+teal: 008080, navy: 000080).
+
+The program should handle invalid hexadecimal strings.
+
+### Submitting Exercises
+
+Note that, when trying to submit an exercise, make sure the exercise file that you're submitting is in the `exercism/csharp/<exerciseName>` directory.
+
+For example, if you're submitting `bob.cs` for the Bob exercise, the submit command would be something like `exercism submit <path_to_exercism_dir>/csharp/bob/bob.cs`.
+## Source
+
+All of Computer Science [http://www.wolframalpha.com/examples/NumberBases.html](http://www.wolframalpha.com/examples/NumberBases.html)
+
+## Submitting Incomplete Solutions
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.
diff --git a/exercises/octal/Example.cs b/exercises/octal/Example.cs
new file mode 100644
index 0000000000..1bfc546e5b
--- /dev/null
+++ b/exercises/octal/Example.cs
@@ -0,0 +1,24 @@
+using System;
+using System.Linq;
+
+public class Octal
+{
+    public static int ToDecimal(string octal)
+    {
+        if (IsNotValidOctal(octal)) return 0;
+
+        return octal
+            .Select((c, i) => int.Parse(c.ToString()) * EightToThePowerOf(octal.Length - i - 1))
+            .Sum();
+    }
+
+    private static bool IsNotValidOctal(string octal)
+    {
+        return !octal.All(x => char.IsDigit(x) && int.Parse(x.ToString()) < 8);
+    }
+
+    private static int EightToThePowerOf(int power)
+    {
+        return (int)Math.Pow(8, power);
+    }
+}
\ No newline at end of file
diff --git a/exercises/octal/Octal.cs b/exercises/octal/Octal.cs
new file mode 100644
index 0000000000..0b1702d96f
--- /dev/null
+++ b/exercises/octal/Octal.cs
@@ -0,0 +1,9 @@
+using System;
+
+public class Octal
+{
+    public static int ToDecimal(string octal)
+    {
+        throw new NotImplementedException("You need to implement this function.");
+    }
+}
diff --git a/exercises/octal/Octal.csproj b/exercises/octal/Octal.csproj
new file mode 100644
index 0000000000..082b3bbe5f
--- /dev/null
+++ b/exercises/octal/Octal.csproj
@@ -0,0 +1,17 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>netcoreapp2.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Remove="Example.cs" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.5.0" />
+    <PackageReference Include="xunit" Version="2.3.1" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.3.1" />
+  </ItemGroup>
+
+</Project>
diff --git a/exercises/octal/OctalTest.cs b/exercises/octal/OctalTest.cs
new file mode 100644
index 0000000000..e1772ff046
--- /dev/null
+++ b/exercises/octal/OctalTest.cs
@@ -0,0 +1,88 @@
+using Xunit;
+
+public class OctalTest
+{
+    [Fact]
+    public void Octal_1_is_decimal_1()
+    {
+        Assert.Equal(1, Octal.ToDecimal("1"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Octal_10_is_decimal_8()
+    {
+        Assert.Equal(8, Octal.ToDecimal("10"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Octal_17_is_decimal_15()
+    {
+        Assert.Equal(15, Octal.ToDecimal("17"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Octal_11_is_decimal_9()
+    {
+        Assert.Equal(9, Octal.ToDecimal("11"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Octal_130_is_decimal_88()
+    {
+        Assert.Equal(88, Octal.ToDecimal("130"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Octal_2047_is_decimal_1063()
+    {
+        Assert.Equal(1063, Octal.ToDecimal("2047"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Octal_7777_is_decimal_4095()
+    {
+        Assert.Equal(4095, Octal.ToDecimal("7777"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Octal_1234567_is_decimal_342391()
+    {
+        Assert.Equal(342391, Octal.ToDecimal("1234567"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Octal_011_is_decimal_9()
+    {
+        Assert.Equal(9, Octal.ToDecimal("011"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Octal_carrot_is_decimal_0()
+    {
+        Assert.Equal(0, Octal.ToDecimal("carrot"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Octal_8_is_decimal_0()
+    {
+        Assert.Equal(0, Octal.ToDecimal("8"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Octal_9_is_decimal_0()
+    {
+        Assert.Equal(0, Octal.ToDecimal("9"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Octal_6789_is_decimal_0()
+    {
+        Assert.Equal(0, Octal.ToDecimal("6789"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Octal_abc1z_is_decimal_0()
+    {
+        Assert.Equal(0, Octal.ToDecimal("abc1z"));
+    }
+}
diff --git a/exercises/octal/README.md b/exercises/octal/README.md
new file mode 100644
index 0000000000..6c7ce83b43
--- /dev/null
+++ b/exercises/octal/README.md
@@ -0,0 +1,55 @@
+# Octal
+
+Convert an octal number, represented as a string (e.g. '1735263'), to its
+decimal equivalent using first principles (i.e. no, you may not use built-in or
+external libraries to accomplish the conversion).
+
+Implement octal to decimal conversion.  Given an octal input
+string, your program should produce a decimal output.
+
+## Note
+- Implement the conversion yourself.
+  Do not use something else to perform the conversion for you.
+- Treat invalid input as octal 0.
+
+## About Octal (Base-8)
+Decimal is a base-10 system.
+
+A number 233 in base 10 notation can be understood
+as a linear combination of powers of 10:
+
+- The rightmost digit gets multiplied by 10^0 = 1
+- The next number gets multiplied by 10^1 = 10
+- ...
+- The *n*th number gets multiplied by 10^*(n-1)*.
+- All these values are summed.
+
+So:
+```
+   233 # decimal
+ = 2*10^2 + 3*10^1 + 3*10^0
+ = 2*100  + 3*10   + 3*1
+```
+
+Octal is similar, but uses powers of 8 rather than powers of 10.
+
+So:
+```
+   233 # octal
+ = 2*8^2 + 3*8^1 + 3*8^0
+ = 2*64  + 3*8   + 3*1
+ = 128   + 24    + 3
+ = 155
+```
+
+### Submitting Exercises
+
+Note that, when trying to submit an exercise, make sure the exercise file that you're submitting is in the `exercism/csharp/<exerciseName>` directory.
+
+For example, if you're submitting `bob.cs` for the Bob exercise, the submit command would be something like `exercism submit <path_to_exercism_dir>/csharp/bob/bob.cs`.
+## Source
+
+All of Computer Science [http://www.wolframalpha.com/input/?i=base+8](http://www.wolframalpha.com/input/?i=base+8)
+
+## Submitting Incomplete Solutions
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.
diff --git a/exercises/trinary/Example.cs b/exercises/trinary/Example.cs
new file mode 100644
index 0000000000..75bea722da
--- /dev/null
+++ b/exercises/trinary/Example.cs
@@ -0,0 +1,24 @@
+using System;
+using System.Linq;
+
+public class Trinary
+{
+    public static int ToDecimal(string trinary)
+    {
+        if (IsNotValidTrinary(trinary)) return 0;
+
+        return trinary
+            .Select((c, i) => int.Parse(c.ToString()) * ThreeToThePowerOf(trinary.Length - i - 1))
+            .Sum();
+    }
+
+    private static bool IsNotValidTrinary(string trinary)
+    {
+        return !trinary.All(x => char.IsDigit(x) && int.Parse(x.ToString()) < 3);
+    }
+
+    private static int ThreeToThePowerOf(int power)
+    {
+        return (int)Math.Pow(3, power);
+    }
+}
\ No newline at end of file
diff --git a/exercises/trinary/README.md b/exercises/trinary/README.md
new file mode 100644
index 0000000000..fd06c96dba
--- /dev/null
+++ b/exercises/trinary/README.md
@@ -0,0 +1,34 @@
+# Trinary
+
+Convert a trinary number, represented as a string (e.g. '102012'), to its
+decimal equivalent using first principles.
+
+The program should consider strings specifying an invalid trinary as the
+value 0.
+
+Trinary numbers contain three symbols: 0, 1, and 2.
+
+The last place in a trinary number is the 1's place. The second to last
+is the 3's place, the third to last is the 9's place, etc.
+
+```bash
+# "102012"
+    1       0       2       0       1       2    # the number
+1*3^5 + 0*3^4 + 2*3^3 + 0*3^2 + 1*3^1 + 2*3^0    # the value
+  243 +     0 +    54 +     0 +     3 +     2 =  302
+```
+
+If your language provides a method in the standard library to perform the
+conversion, pretend it doesn't exist and implement it yourself.
+
+### Submitting Exercises
+
+Note that, when trying to submit an exercise, make sure the exercise file that you're submitting is in the `exercism/csharp/<exerciseName>` directory.
+
+For example, if you're submitting `bob.cs` for the Bob exercise, the submit command would be something like `exercism submit <path_to_exercism_dir>/csharp/bob/bob.cs`.
+## Source
+
+All of Computer Science [http://www.wolframalpha.com/input/?i=binary&a=*C.binary-_*MathWorld-](http://www.wolframalpha.com/input/?i=binary&a=*C.binary-_*MathWorld-)
+
+## Submitting Incomplete Solutions
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.
diff --git a/exercises/trinary/Trinary.cs b/exercises/trinary/Trinary.cs
new file mode 100644
index 0000000000..972813de31
--- /dev/null
+++ b/exercises/trinary/Trinary.cs
@@ -0,0 +1,9 @@
+using System;
+
+public class Trinary
+{
+    public static int ToDecimal(string trinary)
+    {
+        throw new NotImplementedException("You need to implement this function.");
+    }
+}
diff --git a/exercises/trinary/Trinary.csproj b/exercises/trinary/Trinary.csproj
new file mode 100644
index 0000000000..082b3bbe5f
--- /dev/null
+++ b/exercises/trinary/Trinary.csproj
@@ -0,0 +1,17 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>netcoreapp2.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Remove="Example.cs" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.5.0" />
+    <PackageReference Include="xunit" Version="2.3.1" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.3.1" />
+  </ItemGroup>
+
+</Project>
diff --git a/exercises/trinary/TrinaryTest.cs b/exercises/trinary/TrinaryTest.cs
new file mode 100644
index 0000000000..2dea45fe6a
--- /dev/null
+++ b/exercises/trinary/TrinaryTest.cs
@@ -0,0 +1,70 @@
+using Xunit;
+
+public class TrinaryTest
+{
+    [Fact]
+    public void Trinary_1_is_decimal_1()
+    {
+        Assert.Equal(1, Trinary.ToDecimal("1"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Trinary_2_is_decimal_2()
+    {
+        Assert.Equal(2, Trinary.ToDecimal("2"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Trinary_10_is_decimal_3()
+    {
+        Assert.Equal(3, Trinary.ToDecimal("10"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Trinary_11_is_decimal_4()
+    {
+        Assert.Equal(4, Trinary.ToDecimal("11"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Trinary_100_is_decimal_9()
+    {
+        Assert.Equal(9, Trinary.ToDecimal("100"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Trinary_112_is_decimal_14()
+    {
+        Assert.Equal(14, Trinary.ToDecimal("112"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Trinary_222_is_decimal_26()
+    {
+        Assert.Equal(26, Trinary.ToDecimal("222"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Trinary_1122000120_is_decimal_32091()
+    {
+        Assert.Equal(32091, Trinary.ToDecimal("1122000120"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Invalid_trinary_digits_returns_0()
+    {
+        Assert.Equal(0, Trinary.ToDecimal("1234"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Invalid_word_as_input_returns_0()
+    {
+        Assert.Equal(0, Trinary.ToDecimal("carrot"));
+    }
+
+    [Fact(Skip = "Remove to run test")]
+    public void Invalid_numbers_with_letters_as_input_returns_0()
+    {
+        Assert.Equal(0, Trinary.ToDecimal("0a1b2c"));
+    }
+}