[Solved] Set watermark For TextBox in Windows Application using C# and VB.Net

Hi kana250688,

You can use Enter and Leave event handlers of TextBox.

Refer below code.

Form

Code

C#

string FirstName_DefaultText = "Enter First Name";
string LastName_DefaultText = "Enter Last Name";
private void Form1_Load(object sender, EventArgs e)
{
    txtFirstName.ForeColor = Color.Gray;
    if (string.IsNullOrEmpty(txtFirstName.Text))
    {
        txtFirstName.Text = this.FirstName_DefaultText;
    }

    txtLastName.ForeColor = Color.Gray;
    if (string.IsNullOrEmpty(txtLastName.Text))
    {
        txtLastName.Text = this.LastName_DefaultText;
    }
}

private void txtFirstName_Enter(object sender, EventArgs e)
{
    txtFirstName.ForeColor = Color.Black;
    if (txtFirstName.Text == this.FirstName_DefaultText)
    {
        txtFirstName.Text = string.Empty;
    }
}

private void txtLastName_Enter(object sender, EventArgs e)
{
    txtLastName.ForeColor = Color.Black;
    if (txtLastName.Text == this.LastName_DefaultText)
    {
        txtLastName.Text = string.Empty;
    }
}


private void txtFirstName_Leave(object sender, EventArgs e)
{
    if (string.IsNullOrEmpty(txtFirstName.Text.Trim()))
    {
        txtFirstName.ForeColor = Color.Gray;
        txtFirstName.Text = this.FirstName_DefaultText;
    }
}


private void txtLastName_Leave(object sender, EventArgs e)
{
    if (string.IsNullOrEmpty(txtLastName.Text.Trim()))
    {
        txtLastName.ForeColor = Color.Gray;
        txtLastName.Text = this.LastName_DefaultText;
    }
}

VB.Net

Private FirstName_DefaultText As String = "Enter First Name"
Private LastName_DefaultText As String = "Enter Last Name"

Private Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs) Handles MyBase.Load
    txtFirstName.ForeColor = Color.Gray

    If String.IsNullOrEmpty(txtFirstName.Text) Then
        txtFirstName.Text = Me.FirstName_DefaultText
    End If

    txtLastName.ForeColor = Color.Gray

    If String.IsNullOrEmpty(txtLastName.Text) Then
        txtLastName.Text = Me.LastName_DefaultText
    End If
End Sub

Private Sub txtFirstName_Enter(ByVal sender As Object, ByVal e As EventArgs) Handles txtFirstName.Enter
    txtFirstName.ForeColor = Color.Black

    If txtFirstName.Text = Me.FirstName_DefaultText Then
        txtFirstName.Text = String.Empty
    End If
End Sub

Private Sub txtLastName_Enter(ByVal sender As Object, ByVal e As EventArgs) Handles txtLastName.Enter
    txtLastName.ForeColor = Color.Black

    If txtLastName.Text = Me.LastName_DefaultText Then
        txtLastName.Text = String.Empty
    End If
End Sub

Private Sub txtFirstName_Leave(ByVal sender As Object, ByVal e As EventArgs) Handles txtFirstName.Leave
    If String.IsNullOrEmpty(txtFirstName.Text.Trim()) Then
        txtFirstName.ForeColor = Color.Gray
        txtFirstName.Text = Me.FirstName_DefaultText
    End If
End Sub

Private Sub txtLastName_Leave(ByVal sender As Object, ByVal e As EventArgs) Handles txtLastName.Leave
    If String.IsNullOrEmpty(txtLastName.Text.Trim()) Then
        txtLastName.ForeColor = Color.Gray
        txtLastName.Text = Me.LastName_DefaultText
    End If
End Sub

Screenshot