CA1834 Consider using 'StringBuilder.Append(char)' when applicable

eng/Common.globalconfig

@@ -307,7 +307,7 @@ dotnet_diagnostic.CA1832.severity = warning
 dotnet_diagnostic.CA1833.severity = warning
 
 # Consider using 'StringBuilder.Append(char)' when applicable.
-dotnet_diagnostic.CA1834.severity = suggestion
+dotnet_diagnostic.CA1834.severity = warning
 
 # Prefer the 'Memory'-based overloads for 'ReadAsync' and 'WriteAsync'
 dotnet_diagnostic.CA1835.severity = suggestion

src/Build.UnitTests/Evaluation/ProjectStringCache_Tests.cs

@@ -286,7 +286,7 @@ public void AddReturnsSameInstanceForSameDocument()
             // Build a new string guaranteed not to be optimized by the compiler into the same instance.
             StringBuilder builder = new StringBuilder();
             builder.Append("Test");
-            builder.Append("1");
+            builder.Append('1');
 
             string return2 = cache.Add(builder.ToString(), document);
 
@@ -320,7 +320,7 @@ public void AddReturnsSameInstanceForDifferentDocument()
             // Build a new string guaranteed not to be optimized by the compiler into the same instance.
             StringBuilder builder = new StringBuilder();
             builder.Append("Test");
-            builder.Append("1");
+            builder.Append('1');
             XmlDocument document2 = new XmlDocument();
 
             string return2 = cache.Add(builder.ToString(), document2);
@@ -362,7 +362,7 @@ public void RemoveLastInstanceDeallocatesEntry()
             // Build a new string guaranteed not to be optimized by the compiler into the same instance.
             StringBuilder builder = new StringBuilder();
             builder.Append("Test");
-            builder.Append("1");
+            builder.Append('1');
             XmlDocument document2 = new XmlDocument();
 
             string return2 = cache.Add(builder.ToString(), document2);
@@ -399,7 +399,7 @@ public void RemoveOneInstance()
             // Build a new string guaranteed not to be optimized by the compiler into the same instance.
             StringBuilder builder = new StringBuilder();
             builder.Append("Test");
-            builder.Append("1");
+            builder.Append('1');
             XmlDocument document3 = new XmlDocument();
 
             string return3 = cache.Add(builder.ToString(), document3);
@@ -434,7 +434,7 @@ public void DifferentStringsSameDocument()
             // Build a new string guaranteed not to be optimized by the compiler into the same instance.
             StringBuilder builder = new StringBuilder();
             builder.Append("Test");
-            builder.Append("2");
+            builder.Append('2');
             string return3 = cache.Add(builder.ToString(), document);
 
             // The new string should be the same as the other one already in the collection.
@@ -468,7 +468,7 @@ public void DifferentStringsDifferentDocuments()
             // Build a new string guaranteed not to be optimized by the compiler into the same instance.
             StringBuilder builder = new StringBuilder();
             builder.Append("Test");
-            builder.Append("2");
+            builder.Append('2');
             XmlDocument document3 = new XmlDocument();
             string return3 = cache.Add(builder.ToString(), document3);
 

src/Build/Construction/Solution/SolutionProjectGenerator.cs

@@ -1779,7 +1779,7 @@ private string ComputeTargetConditionForWebProject(ProjectInSolution project)
                     {
                         condition.Append(" or (");
                         condition.Append(GetConditionStringForConfiguration(solutionConfiguration));
-                        condition.Append(")");
+                        condition.Append(')');
                     }
                 }
                 else if (String.Equals(solutionConfiguration.ConfigurationName, "Release", StringComparison.OrdinalIgnoreCase) ||
@@ -1790,7 +1790,7 @@ private string ComputeTargetConditionForWebProject(ProjectInSolution project)
                     // so these should be available in the solution project
                     condition.Append(" or (");
                     condition.Append(GetConditionStringForConfiguration(solutionConfiguration));
-                    condition.Append(")");
+                    condition.Append(')');
                 }
             }
 

src/Build/Graph/ProjectGraph.cs

@@ -524,7 +524,7 @@ internal string ToDot(
                 }
             }
 
-            sb.Append("}");
+            sb.Append('}');
 
             return sb.ToString();
 

src/Framework/BuildEventArgs.cs

@@ -290,14 +290,14 @@ private void SetBuildEventContextDefaultAfterSerialization(StreamingContext sc)
         {
             var sb = new StringBuilder();
             sb.Append(resourceName);
-            sb.Append("(");
+            sb.Append('(');
 
             bool notFirst = false;
             foreach (var argument in arguments)
             {
                 if (notFirst)
                 {
-                    sb.Append(",");
+                    sb.Append(',');
                 }
                 else
                 {
@@ -307,7 +307,7 @@ private void SetBuildEventContextDefaultAfterSerialization(StreamingContext sc)
                 sb.Append(argument);
             }
 
-            sb.Append(")");
+            sb.Append(')');
             return sb.ToString();
         };
 

src/MSBuild/XMake.cs

@@ -187,9 +187,9 @@ private static void HandleConfigurationException(Exception ex)
                 // One of the exceptions is missing a period!
                 if (message[message.Length - 1] != '.')
                 {
-                    builder.Append(".");
+                    builder.Append('.');
                 }
-                builder.Append(" ");
+                builder.Append(' ');
 
                 exception = exception.InnerException;
             }

src/Shared/ExceptionHandling.cs

@@ -373,7 +373,7 @@ internal static string ReadAnyExceptionFromFile(DateTime fromTimeUtc)
                 {
                     builder.Append(Environment.NewLine);
                     builder.Append(file);
-                    builder.Append(":");
+                    builder.Append(':');
                     builder.Append(Environment.NewLine);
                     builder.Append(File.ReadAllText(file));
                     builder.Append(Environment.NewLine);

src/Shared/FileMatcher.cs

@@ -2228,7 +2228,7 @@ internal static string Normalize(string aString)
             }
             else if (aString.StartsWith(@"\", StringComparison.Ordinal))
             {
-                sb.Append(@"\");
+                sb.Append('\\');
                 index = SkipSlashes(aString, 1);
             }
 

src/Tasks.UnitTests/ResourceHandling/GenerateResource_Tests.cs

@@ -3618,7 +3618,7 @@ public static string GetTestTextContent(string tagName, string oneLine, bool cle
 
             if (tagName != null)
             {
-                txt.Append("[");
+                txt.Append('[');
                 txt.Append(tagName);
                 txt.Append("]\xd\xa");
             }

src/Utilities/CommandLineBuilder.cs

@@ -222,7 +222,7 @@ protected void AppendSpaceIfNotEmpty()
                 }
                 else if(CommandLine[CommandLine.Length - 1] != ' ')
                 {
-                    CommandLine.Append(" ");
+                    CommandLine.Append(' ');
                 }
             }
         }

src/Utilities/ToolLocationHelper.cs

@@ -2303,12 +2303,12 @@ public static string GetDisplayNameForTargetFrameworkDirectory(string targetFram
             StringBuilder displayNameBuilder = new StringBuilder();
 
             displayNameBuilder.Append(frameworkName.Identifier);
-            displayNameBuilder.Append(" ");
+            displayNameBuilder.Append(' ');
             displayNameBuilder.Append('v').Append(frameworkName.Version.ToString());
 
             if (!string.IsNullOrEmpty(frameworkName.Profile))
             {
-                displayNameBuilder.Append(" ");
+                displayNameBuilder.Append(' ');
                 displayNameBuilder.Append(frameworkName.Profile);
             }