Hook up callsite column

src/VisualStudio/Core/Def/Implementation/ChangeSignature/ChangeSignatureDialog.xaml

@@ -210,6 +210,13 @@
                             </Style>
                         </DataGridTextColumn.ElementStyle>
                     </DataGridTextColumn>
+                    <DataGridTextColumn x:Name="callsiteHeader" Binding="{Binding Callsite, Mode=OneWay}" Width="*" IsReadOnly="True">
+                        <DataGridTextColumn.ElementStyle>
+                            <Style TargetType="TextBlock">
+                                <Setter Property="Padding" Value="{StaticResource ResourceKey=cellPadding}" />
+                            </Style>
+                        </DataGridTextColumn.ElementStyle>
+                    </DataGridTextColumn>
                 </DataGrid.Columns>
             </DataGrid>
 

src/VisualStudio/Core/Def/Implementation/ChangeSignature/ChangeSignatureDialogViewModel.cs

@@ -505,6 +505,7 @@ public abstract class ParameterViewModel
             public abstract bool IsRemoved { get; set; }
             public abstract string ParameterAutomationText { get; }
             public abstract bool IsDisabled { get; }
+            public abstract string Callsite { get; }
 
             public ParameterViewModel(ChangeSignatureDialogViewModel changeSignatureDialogViewModel)
             {
@@ -530,6 +531,7 @@ public AddedParameterViewModel(ChangeSignatureDialogViewModel changeSignatureDia
 
             public override string ParameterAutomationText => $"{Type} {Parameter}";
             public override bool IsDisabled => false;
+            public override string Callsite => _addParameterViewModel.CallsiteValue;
         }
 
         public class ExistingParameterViewModel : ParameterViewModel
@@ -547,6 +549,8 @@ public ExistingParameterViewModel(ChangeSignatureDialogViewModel changeSignature
 
             public override string ParameterAutomationText => $"{Type} {Parameter}";
 
+            public override string Callsite => string.Empty;
+
             public string Modifier
             {
                 get