检查TextBox是否为空并返回MessageBox？
我做了这个语句来检查TextBox是否为空，但MessageBox总是显示TextBox是否为空。
private void NextButton_Click(object sender, EventArgs e) { decimal MarkPoints, x, y; x = HoursNumericUpDown.Value; y = MarkNumericUpDown.Value; MarkPoints = x * y; //decimal MarkPoints = (decimal)HoursNumericUpDown.Value * (decimal)HoursNumericUpDown.Value; DataGridViewRow dgvRow = new DataGridViewRow(); DataGridViewTextBoxCell dgvCell = new DataGridViewTextBoxCell(); dgvCell = new DataGridViewTextBoxCell(); dgvCell.Value = MaterialTextBox.Text; dgvRow.Cells.Add(dgvCell); dgvCell = new DataGridViewTextBoxCell(); dgvCell.Value = HoursNumericUpDown.Value; dgvRow.Cells.Add(dgvCell); dgvCell = new DataGridViewTextBoxCell(); dgvCell.Value = MarkNumericUpDown.Value; dgvRow.Cells.Add(dgvCell); dgvCell = new DataGridViewTextBoxCell(); dgvCell.Value = MarkPoints; dgvRow.Cells.Add(dgvCell); dataGridView1.Rows.Add(dgvRow); MaterialTextBox.Clear(); HoursNumericUpDown.Value = HoursNumericUpDown.Minimum; MarkNumericUpDown.Value = MarkNumericUpDown.Minimum; if (String.IsNullOrEmpty(MaterialTextBox.Text)) { MessageBox.Show("Enter Material Name Please.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Warning); //dataGridView1.Rows.Clear(); } else { /*if (MarkNumericUpDown.Value 50 && MarkNumericUpDown.Value <= 64) { dataGridView1.Rows[index].Cells[4].Value = "F"; }*/ 请尝试这种情况：
if (string.IsNullOrWhiteSpace(MaterialTextBox.Text)) { // Message box }
这将处理一些只包含空白字符的字符串，你不必处理字符串相等，这有时会很棘手
好吧，在检查文本框是否为空之前，您正在清除文本框
/* !! This clears the textbox BEFORE you check if it's empty */ MaterialTextBox.Clear(); HoursNumericUpDown.Value = HoursNumericUpDown.Minimum; MarkNumericUpDown.Value = MarkNumericUpDown.Minimum; if (String.IsNullOrEmpty(MaterialTextBox.Text)) { MessageBox.Show("Enter Material Name Please.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Warning); //dataGridView1.Rows.Clear(); }
使用如下内容：
if (String.IsNullOrEmpty(MaterialTextBox.Text))
尝试执行以下操作
if (String.IsNullOrEmpty(MaterialTextBox.Text) || String.IsNullOrWhiteSpace(MaterialTextBox.Text)) { //do job } else { MessageBox.Show("Please enter correct path"); }
希望能帮助到你
加上@ tjg184所说的，你可以做点什么……
if (String.IsNullOrEmpty(MaterialTextBox.Text.Trim()))
…
if (MaterialTextBox.Text.length==0) { message }