From f70b07b8380b48c55eededb6f4426bd5d3bf5a0e Mon Sep 17 00:00:00 2001
From: Steve Smith <steve@kentsmiths.com>
Date: Tue, 1 Aug 2023 14:16:35 -0400
Subject: [PATCH] Fixes #253

---
 .../GuardAgainstExpressionExtensions.cs       | 22 +++++++++++++++++++
 .../GuardAgainstExpression.cs                 | 10 +++++++++
 2 files changed, 32 insertions(+)

diff --git a/src/GuardClauses/GuardAgainstExpressionExtensions.cs b/src/GuardClauses/GuardAgainstExpressionExtensions.cs
index f2cfeacd..ae78d003 100644
--- a/src/GuardClauses/GuardAgainstExpressionExtensions.cs
+++ b/src/GuardClauses/GuardAgainstExpressionExtensions.cs
@@ -50,4 +50,26 @@ public static async Task<T> AgainstExpressionAsync<T>(this IGuardClause guardCla
 
         return input;
     }
+
+    /// <summary>
+    /// Throws an <see cref="ArgumentException" /> if <paramref name="func"/> evaluates to false for given <paramref name="input"/> 
+    /// </summary>
+    /// <typeparam name="T"></typeparam>
+    /// <param name="func"></param>
+    /// <param name="guardClause"></param>
+    /// <param name="input"></param>
+    /// <param name="message"></param>
+    /// <param name="paramName">The name of the parameter that is invalid</param>
+    /// <returns><paramref name="input"/> if the <paramref name="func"/> evaluates to true </returns>
+    /// <exception cref="ArgumentException"></exception>
+    public static T AgainstExpression<T>(this IGuardClause guardClause, Func<T, bool> func,
+        T input, string message, string paramName) where T : struct
+    {
+        if (!func(input))
+        {
+            throw new ArgumentException(message, paramName);
+        }
+
+        return input;
+    }
 }
diff --git a/test/GuardClauses.UnitTests/GuardAgainstExpression.cs b/test/GuardClauses.UnitTests/GuardAgainstExpression.cs
index e5fa6ed2..794ef445 100644
--- a/test/GuardClauses.UnitTests/GuardAgainstExpression.cs
+++ b/test/GuardClauses.UnitTests/GuardAgainstExpression.cs
@@ -74,4 +74,14 @@ public void ErrorMessageMatchesExpected(string customMessage, string expectedMes
         Assert.NotNull(exception.Message);
         Assert.Equal(expectedMessage, exception.Message);
     }
+
+    [Fact]
+    public void ErrorIncludesParamNameIfProvided()
+    {
+        string paramName = "testParamName";
+        var exception = Assert.Throws<ArgumentException>(() => Guard.Against.AgainstExpression(x => x == 1, 2, "custom message", paramName));
+        Assert.NotNull(exception);
+        Assert.NotNull(exception.Message);
+        Assert.Equal(paramName, exception.ParamName);
+    }
 }