Index: Core/Components/src/Core.Components.Gis/Theme/ValueCriterion.cs
===================================================================
diff -u -r2a81f01756e227d5ce93717b21b87e8a5cd5fcbb -r4c7e3ff3bf5c0a50fd9d208b71400e5dfb6cebd4
--- Core/Components/src/Core.Components.Gis/Theme/ValueCriterion.cs	(.../ValueCriterion.cs)	(revision 2a81f01756e227d5ce93717b21b87e8a5cd5fcbb)
+++ Core/Components/src/Core.Components.Gis/Theme/ValueCriterion.cs	(.../ValueCriterion.cs)	(revision 4c7e3ff3bf5c0a50fd9d208b71400e5dfb6cebd4)
@@ -36,7 +36,7 @@
         /// <param name="value">The value to apply when using this criteria.</param>
         /// <exception cref="InvalidEnumArgumentException">Thrown when <paramref name="valueOperator"/>
         /// contains an invalid value for <see cref="ValueCriterionOperator"/>.</exception>
-        public ValueCriterion(ValueCriterionOperator valueOperator, double value)
+        public ValueCriterion(ValueCriterionOperator valueOperator, string value)
         {
             if (!Enum.IsDefined(typeof(ValueCriterionOperator), valueOperator))
             {
@@ -57,6 +57,6 @@
         /// <summary>
         /// Gets the value that belongs to the criteria.
         /// </summary>
-        public double Value { get; }
+        public string Value { get; }
     }
 }
\ No newline at end of file
Index: Core/Components/test/Core.Components.DotSpatial.Test/Converter/FeatureBasedMapDataConverterTest.cs
===================================================================
diff -u -r2a81f01756e227d5ce93717b21b87e8a5cd5fcbb -r4c7e3ff3bf5c0a50fd9d208b71400e5dfb6cebd4
--- Core/Components/test/Core.Components.DotSpatial.Test/Converter/FeatureBasedMapDataConverterTest.cs	(.../FeatureBasedMapDataConverterTest.cs)	(revision 2a81f01756e227d5ce93717b21b87e8a5cd5fcbb)
+++ Core/Components/test/Core.Components.DotSpatial.Test/Converter/FeatureBasedMapDataConverterTest.cs	(.../FeatureBasedMapDataConverterTest.cs)	(revision 4c7e3ff3bf5c0a50fd9d208b71400e5dfb6cebd4)
@@ -525,7 +525,7 @@
             {
                 new CategoryTheme(Color.FromKnownColor(random.NextEnum<KnownColor>()),
                                   new ValueCriterion(random.NextEnum<ValueCriterionOperator>(),
-                                                     random.NextDouble()))
+                                                     "test value"))
             });
 
             var mapData = new TestFeatureBasedMapData("test data")
@@ -562,7 +562,7 @@
             // Setup
             var random = new Random(21);
             const string metadataAttributeName = "Meta";
-            double value = random.NextDouble();
+            const string value = "test value";
 
             var featureScheme = new PointScheme();
             var defaultCategory = new PointCategory();
Index: Core/Components/test/Core.Components.DotSpatial.Test/Converter/MapLineDataConverterTest.cs
===================================================================
diff -u -r2a81f01756e227d5ce93717b21b87e8a5cd5fcbb -r4c7e3ff3bf5c0a50fd9d208b71400e5dfb6cebd4
--- Core/Components/test/Core.Components.DotSpatial.Test/Converter/MapLineDataConverterTest.cs	(.../MapLineDataConverterTest.cs)	(revision 2a81f01756e227d5ce93717b21b87e8a5cd5fcbb)
+++ Core/Components/test/Core.Components.DotSpatial.Test/Converter/MapLineDataConverterTest.cs	(.../MapLineDataConverterTest.cs)	(revision 4c7e3ff3bf5c0a50fd9d208b71400e5dfb6cebd4)
@@ -201,9 +201,9 @@
             var random = new Random(21);
 
             var unequalCriterion = new ValueCriterion(ValueCriterionOperator.UnequalValue,
-                                                      random.NextDouble());
+                                                      "unequal value");
             var equalCriterion = new ValueCriterion(ValueCriterionOperator.EqualValue,
-                                                    random.NextDouble());
+                                                    "equal value");
             var theme = new MapTheme(metadataAttribute, new[]
             {
                 new CategoryTheme(Color.FromKnownColor(random.NextEnum<KnownColor>()),
Index: Core/Components/test/Core.Components.DotSpatial.Test/Converter/MapPointDataConverterTest.cs
===================================================================
diff -u -r2a81f01756e227d5ce93717b21b87e8a5cd5fcbb -r4c7e3ff3bf5c0a50fd9d208b71400e5dfb6cebd4
--- Core/Components/test/Core.Components.DotSpatial.Test/Converter/MapPointDataConverterTest.cs	(.../MapPointDataConverterTest.cs)	(revision 2a81f01756e227d5ce93717b21b87e8a5cd5fcbb)
+++ Core/Components/test/Core.Components.DotSpatial.Test/Converter/MapPointDataConverterTest.cs	(.../MapPointDataConverterTest.cs)	(revision 4c7e3ff3bf5c0a50fd9d208b71400e5dfb6cebd4)
@@ -193,9 +193,9 @@
             var random = new Random(21);
 
             var unequalCriterion = new ValueCriterion(ValueCriterionOperator.UnequalValue,
-                                                      random.NextDouble());
+                                                      "unequal value");
             var equalCriterion = new ValueCriterion(ValueCriterionOperator.EqualValue,
-                                                    random.NextDouble());
+                                                    "equal value");
             var theme = new MapTheme(metadataAttribute, new[]
             {
                 new CategoryTheme(Color.FromKnownColor(random.NextEnum<KnownColor>()),
Index: Core/Components/test/Core.Components.DotSpatial.Test/Converter/MapPolygonDataConverterTest.cs
===================================================================
diff -u -r2a81f01756e227d5ce93717b21b87e8a5cd5fcbb -r4c7e3ff3bf5c0a50fd9d208b71400e5dfb6cebd4
--- Core/Components/test/Core.Components.DotSpatial.Test/Converter/MapPolygonDataConverterTest.cs	(.../MapPolygonDataConverterTest.cs)	(revision 2a81f01756e227d5ce93717b21b87e8a5cd5fcbb)
+++ Core/Components/test/Core.Components.DotSpatial.Test/Converter/MapPolygonDataConverterTest.cs	(.../MapPolygonDataConverterTest.cs)	(revision 4c7e3ff3bf5c0a50fd9d208b71400e5dfb6cebd4)
@@ -280,9 +280,9 @@
             var random = new Random(21);
 
             var unequalCriterion = new ValueCriterion(ValueCriterionOperator.UnequalValue,
-                                                      random.NextDouble());
+                                                      "unequal value");
             var equalCriterion = new ValueCriterion(ValueCriterionOperator.EqualValue,
-                                                    random.NextDouble());
+                                                    "equal value");
             var theme = new MapTheme(metadataAttribute, new[]
             {
                 new CategoryTheme(Color.FromKnownColor(random.NextEnum<KnownColor>()),
Index: Core/Components/test/Core.Components.Gis.Test/Theme/CategoryThemeTest.cs
===================================================================
diff -u -r2a81f01756e227d5ce93717b21b87e8a5cd5fcbb -r4c7e3ff3bf5c0a50fd9d208b71400e5dfb6cebd4
--- Core/Components/test/Core.Components.Gis.Test/Theme/CategoryThemeTest.cs	(.../CategoryThemeTest.cs)	(revision 2a81f01756e227d5ce93717b21b87e8a5cd5fcbb)
+++ Core/Components/test/Core.Components.Gis.Test/Theme/CategoryThemeTest.cs	(.../CategoryThemeTest.cs)	(revision 4c7e3ff3bf5c0a50fd9d208b71400e5dfb6cebd4)
@@ -51,7 +51,7 @@
             // Setup
             var random = new Random(21);
             var criterion = new ValueCriterion(random.NextEnumValue<ValueCriterionOperator>(),
-                                               random.NextDouble());
+                                               "test value");
 
             Color themeColor = Color.FromKnownColor(random.NextEnumValue<KnownColor>());
 
Index: Core/Components/test/Core.Components.Gis.Test/Theme/ValueCriterionTest.cs
===================================================================
diff -u -r2a81f01756e227d5ce93717b21b87e8a5cd5fcbb -r4c7e3ff3bf5c0a50fd9d208b71400e5dfb6cebd4
--- Core/Components/test/Core.Components.Gis.Test/Theme/ValueCriterionTest.cs	(.../ValueCriterionTest.cs)	(revision 2a81f01756e227d5ce93717b21b87e8a5cd5fcbb)
+++ Core/Components/test/Core.Components.Gis.Test/Theme/ValueCriterionTest.cs	(.../ValueCriterionTest.cs)	(revision 4c7e3ff3bf5c0a50fd9d208b71400e5dfb6cebd4)
@@ -36,7 +36,7 @@
             // Setup
             var random = new Random(21);
             var valueOperator = random.NextEnumValue<ValueCriterionOperator>();
-            double value = random.NextDouble();
+            const string value = "test values";
 
             // Call
             var criteria = new ValueCriterion(valueOperator, value);
@@ -50,11 +50,10 @@
         public void Constructor_InvalidOperator_ThrowsInvalidEnumArgumentException()
         {
             // Setup
-            var random = new Random(21);
             const ValueCriterionOperator invalidOperator = (ValueCriterionOperator) 9999;
 
             // Call
-            TestDelegate call = () => new ValueCriterion(invalidOperator, random.NextDouble());
+            TestDelegate call = () => new ValueCriterion(invalidOperator, "test");
 
             // Assert
             string expectedMessage = $"The value of argument 'valueOperator' ({invalidOperator}) is invalid for Enum type '{nameof(ValueCriterionOperator)}'.";
Index: Core/Components/test/Core.Components.Gis.TestUtil/CategoryThemeTestFactory.cs
===================================================================
diff -u -r2a81f01756e227d5ce93717b21b87e8a5cd5fcbb -r4c7e3ff3bf5c0a50fd9d208b71400e5dfb6cebd4
--- Core/Components/test/Core.Components.Gis.TestUtil/CategoryThemeTestFactory.cs	(.../CategoryThemeTestFactory.cs)	(revision 2a81f01756e227d5ce93717b21b87e8a5cd5fcbb)
+++ Core/Components/test/Core.Components.Gis.TestUtil/CategoryThemeTestFactory.cs	(.../CategoryThemeTestFactory.cs)	(revision 4c7e3ff3bf5c0a50fd9d208b71400e5dfb6cebd4)
@@ -40,7 +40,7 @@
             var random = new Random(21);
             return new CategoryTheme(Color.FromKnownColor(random.NextEnumValue<KnownColor>()),
                                      new ValueCriterion(random.NextEnumValue<ValueCriterionOperator>(),
-                                                        random.NextDouble()));
+                                                        "random " + random.Next()));
         }
     }
 }
\ No newline at end of file
Index: Core/Plugins/test/Core.Plugins.Map.Test/PropertyClasses/CategoryThemePropertiesTest.cs
===================================================================
diff -u -r2a81f01756e227d5ce93717b21b87e8a5cd5fcbb -r4c7e3ff3bf5c0a50fd9d208b71400e5dfb6cebd4
--- Core/Plugins/test/Core.Plugins.Map.Test/PropertyClasses/CategoryThemePropertiesTest.cs	(.../CategoryThemePropertiesTest.cs)	(revision 2a81f01756e227d5ce93717b21b87e8a5cd5fcbb)
+++ Core/Plugins/test/Core.Plugins.Map.Test/PropertyClasses/CategoryThemePropertiesTest.cs	(.../CategoryThemePropertiesTest.cs)	(revision 4c7e3ff3bf5c0a50fd9d208b71400e5dfb6cebd4)
@@ -113,11 +113,10 @@
                                                             string formatExpression)
         {
             // Setup
+            var random = new Random(21);
             const string attributeName = "AttributeName";
+            const string value = "random value 123";
 
-            var random = new Random(21);
-            double value = random.NextDouble();
-
             Color color = Color.FromKnownColor(random.NextEnumValue<KnownColor>());
             var criterion = new ValueCriterion(valueOperator, value);
             var theme = new CategoryTheme(color, criterion);