Minor perf tweaks (#5289)

* Avoid creating scriptblocks unnecessarily in PSScriptProperty
* Use string.IsNullOrWhiteSpace instead of Trim().Length

src/Microsoft.PowerShell.Commands.Management/commands/management/WebServiceProxy.cs

@@ -150,7 +150,7 @@ namespace Microsoft.PowerShell.Commands
         /// </summary>
         protected override void BeginProcessing()
         {
-            if (_uri.ToString().Trim().Length == 0)
+            if (string.IsNullOrWhiteSpace(_uri.ToString()))
             {
                 Exception ex = new ArgumentException(WebServiceResources.InvalidUri);
                 ErrorRecord er = new ErrorRecord(ex, "ArgumentException", ErrorCategory.InvalidOperation, null);

src/Microsoft.PowerShell.ConsoleHost/host/msh/ConsoleHost.cs

@@ -2434,7 +2434,7 @@ namespace Microsoft.PowerShell
                             continue;
                         }
 
-                        if (line.Trim().Length == 0)
+                        if (string.IsNullOrWhiteSpace(line))
                         {
                             if (inBlockMode)
                             {

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

@@ -901,7 +901,7 @@ namespace System.Management.Automation
             string resourceId,
             params object[] args)
         {
-            if (String.IsNullOrEmpty(template) || 1 >= template.Trim().Length)
+            if (string.IsNullOrWhiteSpace(template))
             {
                 _textLookupError = PSTraceSource.NewInvalidOperationException(
                     ErrorPackage.ErrorDetailsEmptyTemplate,

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

@@ -195,7 +195,7 @@ namespace System.Management.Automation.Runspaces
         public SessionStateTypeEntry(string fileName)
             : base(fileName)
         {
-            if (String.IsNullOrEmpty(fileName) || fileName.Trim().Length == 0)
+            if (string.IsNullOrWhiteSpace(fileName))
             {
                 throw PSTraceSource.NewArgumentException("fileName");
             }
@@ -300,7 +300,7 @@ namespace System.Management.Automation.Runspaces
         public SessionStateFormatEntry(string fileName)
             : base("*")
         {
-            if (String.IsNullOrEmpty(fileName) || fileName.Trim().Length == 0)
+            if (string.IsNullOrWhiteSpace(fileName))
             {
                 throw PSTraceSource.NewArgumentException("fileName");
             }

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

@@ -1782,7 +1782,7 @@ namespace System.Management.Automation
         {
             get
             {
-                return this.SetterScript != null;
+                return this._setterScript != null || this._setterScriptText != null;
             }
         }
 
@@ -1793,7 +1793,7 @@ namespace System.Management.Automation
         {
             get
             {
-                return this.GetterScript != null;
+                return this._getterScript != null || this._getterScriptText != null;
             }
         }
 

src/System.Management.Automation/engine/hostifaces/Parameter.cs

@@ -49,7 +49,7 @@ namespace System.Management.Automation.Runspaces
         {
             if (name != null)
             {
-                if (name.Trim().Length == 0)
+                if (string.IsNullOrWhiteSpace(name))
                 {
                     throw PSTraceSource.NewArgumentException("name");
                 }
@@ -105,7 +105,7 @@ namespace System.Management.Automation.Runspaces
 
                 Diagnostics.Assert(name != null, "'name' variable should be initialized at this point");
                 Diagnostics.Assert(name[0].IsDash(), "first character in parameter name must be a dash");
-                Diagnostics.Assert(name.Trim().Length != 0, "Parameter name has to have some non-whitespace characters in it");
+                Diagnostics.Assert(name.Trim().Length != 1, "Parameter name has to have some non-whitespace characters in it");
             }
 
             if (internalParameter.ParameterAndArgumentSpecified)