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vb.net复选框无效强制转换异常

select-case radio-button checkbox vb.net

Robert DeSautel · 技术社区 · 7 年前

Select Case True
Case txtFirstName.Text.Length > 0 & chkActive.CheckState
    dgvEmployees.DataSource = employess.FindEmployee(txtFirstName.Text)
    dgvEmployees.Visible = True
Case txtFirstName.Text.Length > 0 & chkActive.CheckState
    dgvEmployees.DataSource = employess.FindEmployee(txtFirstName.Text, , , "Active")
    chkInactive.Enabled = False
    dgvEmployees.Visible = True
Case txtFirstName.Text.Length > 0 & chkInactive.CheckState
    dgvEmployees.DataSource = employess.FindEmployee(txtFirstName.Text, , , "Inactive")
    chkActive.Enabled = False
    dgvEmployees.Visible = True
Case txtLastName.Text.Length > 0 & chkActive.CheckState
    dgvEmployees.DataSource = employess.FindEmployee(, txtLastName.Text)
    dgvEmployees.Visible = True
Case txtLastName.Text.Length > 0 & chkActive.CheckState
    dgvEmployees.DataSource = employess.FindEmployee(, txtLastName.Text, , "Active")
    chkInactive.Enabled = False
    dgvEmployees.Visible = True
Case txtLastName.Text.Length > 0 & chkInactive.CheckState
    dgvEmployees.DataSource = employess.FindEmployee(, txtLastName.Text, , "Inactive")
    chkActive.Enabled = False
    dgvEmployees.Visible = True
Case txtEmpCode.Text.Length > 0 & rdbActive.Checked
    dgvEmployees.DataSource = employess.FindEmployee(, , txtEmpCode.Text)
    dgvEmployees.Visible = True
Case txtEmpCode.Text.Length > 0 & chkActive.Checked
    dgvEmployees.DataSource = employess.FindEmployee(, , txtEmpCode.Text, "Active")
    chkInactive.Enabled = False
    dgvEmployees.Visible = True
Case txtEmpCode.Text.Length > 0 & chkInactive.CheckState = CheckState.Checked
    dgvEmployees.DataSource = employess.FindEmployee(, , txtEmpCode.Text, "Inactive")
    chkActive.Enabled = False
    dgvEmployees.Visible = True
Case Else
    MessageBox.Show("please enter an employee code, firstname or lastname")
End Select

每次调试时,我都会收到单选按钮或复选框的无效强制转换异常,我是否遗漏了什么?

1 回复 | 直到 2 年前

nayrangnu 7 年前

在Visual Basic中, & performs a string concatenation And 或 AndAlso 正如普卢托瓦所提到的。

将是更好的选择,因为如果第一个条件失败,它将跳过对第二个条件的评估。例如,如果 txtFirstName.Text 长度为0时,程序不会费心检查 chkActive.CheckState 极小的 检查效率高一点 chkActive.CheckState 首先,因为这可能比评估快一点。