Improved file attachment handling in assistants & dialogs (#840)

app/MindWork AI Studio/Components/ReadFileContent.razor

@@ -1,11 +1,23 @@
 @inherits MSGComponentBase
-<MudButton StartIcon="@Icons.Material.Filled.Description" OnClick="@(async () => await this.SelectFile())" Variant="Variant.Filled" Class="mb-3" Disabled="@this.Disabled">
-    @if (string.IsNullOrWhiteSpace(this.Text))
-    {
-        @T("Use file content as input")        
-    }
-    else
-    {
-        @this.Text
-    }
-</MudButton>
+
+@if (this.EnableDragDrop)
+{
+    <div @onmouseenter="@this.OnMouseEnter" @onmouseleave="@this.OnMouseLeave">
+        <MudPaper Outlined="true" Class="@this.dragClass">
+            <MudStack Row="true" AlignItems="AlignItems.Center" StretchItems="StretchItems.None" Wrap="Wrap.Wrap">
+                <MudButton StartIcon="@Icons.Material.Filled.Description" OnClick="@(async () => await this.SelectFile())" Variant="Variant.Filled" Disabled="@this.Disabled">
+                    @this.ButtonText
+                </MudButton>
+                <MudText Typo="Typo.body2">
+                    @T("Drop one file here to load its content.")
+                </MudText>
+            </MudStack>
+        </MudPaper>
+    </div>
+}
+else
+{
+    <MudButton StartIcon="@Icons.Material.Filled.Description" OnClick="@(async () => await this.SelectFile())" Variant="Variant.Filled" Class="mb-3" Disabled="@this.Disabled">
+        @this.ButtonText
+    </MudButton>
+}