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Using Data annotation in Model for DateTime

I am using following code to popup calendar for date in my razor view
Model
[DisplayFormat(ApplyFormatInEditMode = true, DataFormatString = "{0:dd/MM/yyyy}")]
[DataType(DataType.Date)]
public Nullable<System.DateTime> EndTime { get; set; }
View
<div class="form-group">
#Html.LabelFor(model => model.EndTime, htmlAttributes: new { #class = "control-label col-md-2" })
<div class="col-md-4">
#Html.EditorFor(model => model.EndTime, new { htmlAttributes = new { #class = "form-control" } })
#Html.ValidationMessageFor(model => model.EndTime, "", new { #class = "text-danger" })
</div>
</div>
Now I want to use DateTime instead of Date.What should be the DataFormat String?
My Try
Display(Name = "End Date Time")]
[DisplayFormat(ApplyFormatInEditMode = true, DataFormatString = "{0:dd/MM/yyyy}{1:HH/mm}")]
[DataType(DataType.DateTime)]
I am getting format exception?

Your EditorFor() method renders an input with type="date" because of the [DataType(DataType.Date)] attribute, which will generate the browsers HTML-5 datepicker (but this is only supported in Chrome and Edge).
To generate a HTML-5 datetimepicker, you need to render an input with type = "datetime-local" but there is no data annotation attribute for that. Instead you need to generate the type attribute yourself.
#Html.TextBoxFor(m => m.EndTime, "{0:s}", new { #type = "datetime-local", #class = "form-control" })
Note "{0:s}" is shortcut for "{0:yyyy-MM-ddTHH:mm:ss}" and will display the date and time in the browsers culture. Note also that you do not need your [DataType] attribute or the ApplyFormatInEditMode = true property in the [DisplayFormat] attribute since they apply only to EditorFor()

Display Datepicker in Editor onload instead of needing the user to pick

currently I have this datepicker which will hightlight today's date on the pop up calender but the editor for the date onLoad shows DD/MM/YYYY instead of aotopopulating it when the page loads. How do I solve this ?
This is how I display my datepicker in the html file:
<div class="form-group">
#Html.LabelFor(model => model.date, htmlAttributes: new { #class = "control-label col-md-2" })
<div class="col-md-10">
#Html.EditorFor(model => model.date)
#Html.ValidationMessageFor(model => model.date)
</div>
</div>
And this is how I define it:
[DataType(DataType.Date)]
[DisplayFormat(ApplyFormatInEditMode = true, DataFormatString = "{0:d}")]

Your EditorFor() method is rendering your browsers HTML-5 implementation of a datepicker, which requires that the format be yyyy-MM-dd (ISO format).
Change the attribute to
[DataType(DataType.Date)]
[DisplayFormat(ApplyFormatInEditMode = true, DataFormatString = "{0:yyyy-MM-dd}")
public DateTime date { get; set; }
which will display the date in the browsers culture
Alternatively you can use
#Html.TextBoxFor(m => m.date, "{0:yyyy-MM-dd}", new { #type = "date" })
if you do not want to change the format that will be used in a DisplayFor() method.
Note also that type="date" is only supported in Chrome and Edge

Issue displaying money on view

I have the following
public decimal? Price {get;set;}
When I enter 3000.00 in to the textbox on the view (textbox below)
<div class="form-group">
<label class="col-lg-3 control-label no-padding-right">Price</label>
<div class="col-lg-5">
#Html.ValidationMessageFor(m => m.Price)
<div class="input-group">
<span class="input-group-addon">£</span>
#Html.TextBoxFor(m => m.Price, new { #class = "form-control", type = "text", id = "txtPrice", onkeypress = "return isNumberKey(event)" })
</div>
</div>
<label class="col-lg-4 control-label" style="text-align: left">Decimal format</label>
So it would look like this
It saves in the database as 3000.00 which is expected, but when I return back to the view to edit it the value in the textbox is 3000.0000
I have tried some of the solutions on here
Remove trailing zeros of decimal
I think the issue I have is the field on the view is of type decimal not a string, so I'm uncertain on how to format this decimal to remove the trailing zeros so it looks like picture above

You need to use the oveload of TextBoxFor that accepts a format string
#Html.TextBoxFor(m => m.Price, "{0:0.00}", new { #class = "form-control", type = "text", id = "txtPrice", onkeypress = "return isNumberKey(event)"})
Side notes:
Remove type="text". The html helper already adds this for you (add
is there a reason why you dont just use the default id rendered by
the helper, which would be id="Price"?).
Use Unobtrusive Javascript rather that polluting your markup
with behavior - e.g. $('#txtPrice').keypress(...

ASP.NET MVC Client Side Validation Message Error

Can somebody tell me why "This field is required" and "Please insert database name" are being displayed instead of just "Please insert database name"?
This is my model :
public class InstallViewModel
{
[Required(AllowEmptyStrings = false, ErrorMessage = "Please insert database name")]
public string DatabaseName { get; set; }
and this is my view :
<div class="input-group">
<span class="input-group-addon">Database</span>
#Html.TextBoxFor(w => w.DatabaseName, new { #class = "form-control", placeholder = "Database name" })
</div>
#Html.ValidationMessageFor(w=> w.DatabaseName)
Thank you.
EDIT:
Can you see the image attached ? I have some problems uploading images.
The view is a partial view and this is the whole partial view:
#Html.ValidationMessageFor(w => w.DatabaseName)
<div class="input-group">
<span class="input-group-addon">Database</span>
#Html.TextBoxFor(w => w.DatabaseName, new { #class = "form-control", placeholder = "Database name" })
</div>
<br />
#Html.CheckBoxFor(w => w.UseWindowsAuthentication, new { #checked = "checked" }) Use Windows Authentication<br /><br />
<div class="wizard-sqlauth" style="display: none">
<div class="input-group">
<span class="input-group-addon">User name</span>
#Html.TextBoxFor(w => w.UserName, new { #class = "form-control", placeholder = "User name" })
</div>
#Html.ValidationMessageFor(w => w.UserName)<br />
<div class="input-group">
<span class="input-group-addon">Password</span>
#Html.PasswordFor(w => w.Password, new { #class = "form-control" })
</div>
#Html.ValidationMessageFor(w => w.Password)
</div>

DatabaseName is "Required" and your input is empty. (There is only placeholder text)

Are you calling jquery validation "manually" anywhere in javascript, i.e.
$('#myform').valid() ?
That would trigger the default value for the required rule ("This field is required."), and would append it as a label after the input, which is exactly the behavior your are experiencing.
If you really need to use both (MVC's Unobstrusive validation + jQuery validation) you can configure jquery validation to ignore certain fields, for example
$('#myform').validate({
ignore: '#databasefieldId'
});

You have applied the RequiredAttribute attribute to a property to the property DatabaseName which implies that the property must contain a value.
A validation exception is raised if the property is null, an empty string (""), or contains only white-space characters.

You just add #Html.ValidationMessageFor(w=> w.DatabaseName) in the top of div. This will show the summary.

Auto Tooltip Validation in MVC 4?

Where the heck are these things coming from? I like them, and I would like to leverage them elsewhere in my site. It appears they only show when I do regular expression validation in model:
[Display(Name = "Residential")]
[RegularExpression(#"[-+]?[0-9]*\.?[0-9]?[0-9]", ErrorMessage = "Must be a number")]
public Byte? residentialExperience { get; set; }
<div class="editor-label row">
#Html.LabelFor(model => model.residentialExperience)
</div>
<div class="editor-field row">
#Html.EditorFor(model => model.residentialExperience)
#Html.ValidationMessageFor(model => model.residentialExperience)
</div>
How can I use these validation tooltips elsewhere? Also, how can I turn them off?
Also: It's not displaying the same message as I have in my model. It says, "Please enter a number" whereas I have written "Must be a number."

This is because you are outputting a numeric field. If you look at your HTML you will see that you have something like this:
<input type="number" ... />
By defining the type as a numbber, the browser knows what to expect and it will give you a generic message. This is part of Html 5 spec.
If you want to override the default behavior you could do this:
#Html.TextBoxFor(model => model.residentialExperience, new { #type = "text" })