Replace some string.Join(string) calls with string.Join(char) (#18411)

src/Microsoft.PowerShell.Commands.Utility/commands/utility/AddType.cs

@@ -110,7 +110,7 @@ namespace Microsoft.PowerShell.Commands
 
                 if (value != null)
                 {
-                    _sourceCode = string.Join("\n", value);
+                    _sourceCode = string.Join('\n', value);
                 }
             }
         }

src/System.Management.Automation/engine/CommandCompletion/CompletionCompleters.cs

@@ -6206,7 +6206,7 @@ namespace System.Management.Automation
             {
                 memberName = methodCacheEntry[0].method.Name;
                 isMethod = true;
-                getToolTip = () => string.Join("\n", methodCacheEntry.methodInformationStructures.Select(static m => m.methodDefinition));
+                getToolTip = () => string.Join('\n', methodCacheEntry.methodInformationStructures.Select(static m => m.methodDefinition));
             }
 
             var psMemberInfo = member as PSMemberInfo;

src/System.Management.Automation/engine/InitialSessionState.cs

@@ -2781,7 +2781,7 @@ namespace System.Management.Automation.Runspaces
                         break;
 
                     case "ValidatePattern":
-                        string pattern = "^(" + string.Join("|", parameterValidationValues) + ")$";
+                        string pattern = "^(" + string.Join('|', parameterValidationValues) + ")$";
                         ValidatePatternAttribute validatePattern = new ValidatePatternAttribute(pattern);
                         metadata.Parameters[parameterName].Attributes.Add(validatePattern);
                         break;

src/System.Management.Automation/engine/Modules/NewModuleManifestCommand.cs

@@ -963,7 +963,7 @@ namespace Microsoft.PowerShell.Commands
 
             if (CompatiblePSEditions != null && (CompatiblePSEditions.Distinct(StringComparer.OrdinalIgnoreCase).Count() != CompatiblePSEditions.Length))
             {
-                string message = StringUtil.Format(Modules.DuplicateEntriesInCompatiblePSEditions, string.Join(",", CompatiblePSEditions));
+                string message = StringUtil.Format(Modules.DuplicateEntriesInCompatiblePSEditions, string.Join(',', CompatiblePSEditions));
                 var ioe = new InvalidOperationException(message);
                 var er = new ErrorRecord(ioe, "Modules_DuplicateEntriesInCompatiblePSEditions", ErrorCategory.InvalidArgument, CompatiblePSEditions);
                 ThrowTerminatingError(er);

src/System.Management.Automation/engine/Modules/SwitchProcessCommand.cs

@@ -80,7 +80,7 @@ namespace Microsoft.PowerShell.Commands
                                 System.Globalization.CultureInfo.InvariantCulture,
                                 CommandBaseStrings.ExecFailed,
                                 Marshal.GetLastPInvokeError(),
-                                string.Join(" ", WithCommand)
+                                string.Join(' ', WithCommand)
                             )
                         ),
                         "ExecutionFailed",

src/System.Management.Automation/engine/parser/PSType.cs

@@ -1434,7 +1434,7 @@ namespace System.Management.Automation.Language
 
             nameParts.Reverse();
             nameParts.Add(typeDefinitionAst.Name);
-            return string.Join(".", nameParts);
+            return string.Join('.', nameParts);
         }
 
         private static readonly OpCode[] s_ldc =

src/System.Management.Automation/engine/remoting/commands/CustomShellCommands.cs

@@ -1462,7 +1462,7 @@ else
         {
             if (groups == null) { return string.Empty; }
 
-            return string.Join(";", groups);
+            return string.Join(';', groups);
         }
 
         /// <summary>

src/System.Management.Automation/engine/remoting/common/RunspaceConnectionInfo.cs

@@ -2470,7 +2470,7 @@ namespace System.Management.Automation.Runspaces
             var argvList = new List<string>();
             argvList.Add(psi.FileName);
 
-            var argsToParse = String.Join(" ", psi.ArgumentList).Trim();
+            var argsToParse = String.Join(' ', psi.ArgumentList).Trim();
             var argsLength = argsToParse.Length;
             for (int i = 0; i < argsLength; )
             {

src/System.Management.Automation/engine/serialization.cs

@@ -1632,7 +1632,7 @@ namespace System.Management.Automation
                 instanceMetadata.Properties.Add(
                     new PSNoteProperty(
                         InternalDeserializer.CimModifiedProperties,
-                        string.Join(" ", namesOfModifiedProperties)));
+                        string.Join(' ', namesOfModifiedProperties)));
             }
         }
 

src/System.Management.Automation/logging/MshLog.cs

@@ -771,7 +771,7 @@ namespace System.Management.Automation
                 logContext.HostId = (string)executionContext.EngineHostInterface.InstanceId.ToString();
             }
 
-            logContext.HostApplication = string.Join(" ", Environment.GetCommandLineArgs());
+            logContext.HostApplication = string.Join(' ', Environment.GetCommandLineArgs());
 
             if (executionContext.CurrentRunspace != null)
             {