Putting if and else in Foreach loop in ASP.NET MVC C#

It's not a good idea to mix partial html fragments with conditional C#/Razor code. The code might repeat but it's far easier to read and maintain later.

I may not have captured your intent correctly, but I can read this and understand how the condition affects the output.

@foreach (var item in Model)
{
    var HeaderImage = item.HeaderPath;

    if (image != "")
    {
        var fileSavePath = Path.Combine(@"\\mainPage.com", "");
        <div class="picGallery">
            <img src="@Url.Content(item.HeaderPath)" alt="Image" />

            <a href="@Url.Action("ViewPage", "Home")">
            </a>
            <div class="desc2">
                <p style="font-size: 13;">@item.Text</p>
                <p style="font-size: 13;">@item.text_2</p>
            </div>
        </div>
    }
    else
    {
        <div class="picGallery">
            <img src="@Url.Content(item.HeaderPath)" alt="Image" />

            <a href="@Url.Action("ViewPage", "Home")">
                <div id="scanIcon">
                    <img src=img.png alt="imageView" />
                    <h1 style="font-size: 10px;">View Image</h1>
                </div>
            </a>
            <div class="desc2">
                <p style="font-size: 13;">@item.Text</p>
                <p style="font-size: 13;">@item.text_2</p>
            </div>
        </div>
    }
}

You can shorten this. But you need to be careful to escape the @if the nested blocks of code within html. It also becomes more difficult to understand what the output should be.

@foreach (var item in Model)
{
    var HeaderImage = item.HeaderPath;

    <div class="picGallery">
        <img src="@Url.Content(item.HeaderPath)" alt="Image" />

        <a href="@Url.Action("ViewPage", "Home")">
            @if (image != "")
            {
                // image exists
                var fileSavePath = Path.Combine(@"\\mainPage.com", "");

                <div>  </div>
            }
            else
            {
                <div id="scanIcon">
                    <img src=img.png alt="imageView" />
                    <h1 style="font-size: 10px;">View Image</h1>
                </div>
            }
        </a>
        <div class="desc2">
            <p style="font-size: 13;">@item.Text</p>
        </div>
    </div>
}